Buffering the table
guyz!
hope this post finds u all at high on spirit. over here, i am having a requirement to buffer one custom table. let me give the scenario of table access. here it goes:
1. it gets updated every month.
2. after getting updated, it is accessed.
3. i also believe that, table size is also small, i.e. size category = 0.
4. finally the access is like, mostly it will retreive only one month data, by taking all the key fields. in my case there are 5 key fields.
so can any one suggest me, which buffering type to use.
manas
Hi,
select 'Buffering not allowed ' button for mentioned case.
Check this help:
Buffering status
Definition
The buffering status specifies whether or not a table may be buffered.
This depends on how the table is used, for example on the expected volume of data in the table or on the type of access to a table. (mainly read or mainly write access to the table. In the latter case, for example, one would not select buffering).
You should therefore select
- Buffering not allowed if a table may not be buffered.
- Buffering allowed but not activated if buffering is
principally allowed for a table, but at the moment no buffering
should be active. The
buffering type specified in this case is only
a suggestion.
- Buffering allowed if the table should be buffered. In this
case a buffering type
must be specified.
The buffering type defines whether and how the table should be buffered.
There are the following types of buffering:
single-record buffering
generic area buffering
full buffering
In generic area buffering, a number of key fields between 1 and no. of key fields-1 must be specified.
Regards
Appana
Similar Messages
-
When it is beter to buffer the table
hi
when it is beter to buffer the tableHi
<b>Table buffering</b>
Advantages of buffering
Concept of buffering
Buffering types
Buffer synchronization
<b>Database access using Buffer concept</b>
Buffering allows you to access data quicker by letting you
access it from the application server instead of the database.
<b>Advantages of buffering</b>
Table buffering increases the performance when the records of the table are read.
As records of a buffered table are read directly from the local buffer of the application server on which the accessing transaction is running, time required to access data is greatly reduced. The access improves by a factor of 10 to 100 depending on the structure of the table and on the exact system configuration.
If the storage requirements in the buffer increase due to further data, the data that has not been accessed for the longest time is displaced. This displacement takes place asynchronously at certain times which are defined dynamically based on the buffer accesses. Data is only displaced if the free space in the buffer is less than a predefined value or the quality of the access is not satisfactory at this time.
Entering $TAB in the command field resets the table buffers on the corresponding application server. Only use this command if there are inconsistencies in the buffer. In large systems, it can take several hours to fill the buffers. The performance is considerably reduced during this time.
<b>Concept of buffering</b>
The R/3 System manages and synchronizes the buffers on the individual application servers. If an application program accesses data of a table, the database interfaces determines whether this data lies in the buffer of the application server. If this is the case, the data is read directly from the buffer. If the data is not in the buffer of the application server, it is read from the database and loaded into the buffer. The buffer can therefore satisfy the next access to this data.
The buffering type determines which records of the table are loaded into the buffer of the application server when a record of the table is accessed. There are three different buffering types.
With full buffering, all the table records are loaded into the buffer when one record of the table is accessed.
With generic buffering, all the records whose left-justified part of the key is the same are loaded into the buffer when a table record is accessed.
With single-record buffering, only the record that was accessed is loaded into the buffer.
<b>Buffering types</b>
With full buffering, the table is either completely or not at all in the buffer. When a record of the table is accessed, all the records of the table are loaded into the buffer.
When you decide whether a table should be fully buffered, you must take the table size, the number of read accesses and the number of write accesses into consideration. The smaller the table is, the more frequently it is read and the less frequently it is written, the better it is to fully buffer the table.
Full buffering is also advisable for tables having frequent accesses to records that do not exist. Since all the records of the table reside in the buffer, it is already clear in the buffer whether or not a record exists.
The data records are stored in the buffer sorted by table key. When you access the data with SELECT, only fields up to the last specified key field can be used for the access. The left-justified part of the key should therefore be as large as possible for such accesses. For example, if the first key field is not defined, the entire table is scanned in the buffer. Under these circumstances, a direct access to the database could be more efficient if there is a suitable secondary index there.
With generic buffering, all the records whose generic key fields agree with this record are loaded into the buffer when one record of the table is accessed. The generic key is a left-justified part of the primary key of the table that must be defined when the buffering type is selected. The generic key should be selected so that the generic areas are not too small, which would result in too many generic areas. If there are only a few records for each generic area, full buffering is usually preferable for the table. If you choose too large a generic key, too much data will be invalidated if there are changes to table entries, which would have a negative effect on the performance.
A table should be generically buffered if only certain generic areas of the table are usually needed for processing.
Client-dependent, fully buffered tables are automatically generically buffered. The client field is the generic key. It is assumed that not all of the clients are being processed at the same time on one application server. Language-dependent tables are a further example of generic buffering. The generic key includes all the key fields up to and including the language field.
The generic areas are managed in the buffer as independent objects. The generic areas are managed analogously to fully buffered tables. You should therefore also read the information about full buffering.
Single-record buffering is recommended particularly for large tables in which only a few records are accessed repeatedly with SELECT SINGLE. All the accesses to the table that do not use SELECT SINGLE bypass the buffer and directly access the database.
If you access a record that was not yet buffered using SELECT SINGLE, there is a database access to load the record. If the table does not contain a record with the specified key, this record is recorded in the buffer as non-existent. This prevents a further database access if you make another access with the same key
You only need one database access to load a table with full buffering, but you need several database accesses with single-record buffering. Full buffering is therefore generally preferable for small tables that are frequently accessed.
<b>Synchronizing local buffers</b>
The table buffers reside locally on each application server in the system. However, this makes it necessary for the buffer administration to transfer all changes made to buffered objects to all the application servers of the system.
If a buffered table is modified, it is updated synchronously in the buffer of the application server from which the change was made. The buffers of the whole network, that is, the buffers of all the other application servers, are synchronized with an asynchronous procedure.
Entries are written in a central database table (DDLOG) after each table modification that could be buffered. Each application server reads these entries at fixed time intervals.
If entries are found that show a change to the data buffered by this server, this data is invalidated. If this data is accessed again, it is read directly from the database. In such an access, the table can then be loaded to the buffer again.
<b>Using buffered tables improves the performance considerably.</b>
Bypassing the buffer increases the network considerably
SELECT SINGLE * FROM T100 INTO T100_WA
BYPASSING BUFFER
WHERE SPRSL = 'D'
AND ARBGB = '00'
AND MSGNR = '999'.
The above mentioned code can be more optimized by using the following code
SELECT SINGLE * FROM T100 INTO T100_WA
WHERE SPRSL = 'D'
AND ARBGB = '00'
AND MSGNR = '999'.
<b>Optimizing the load of the database</b>
<b>Using table buffering</b>
Using buffered tables improves the performance considerably. Note that in some cases a statement can not be used with a buffered table, so when using these statements the buffer will be bypassed. These statements are:
Select DISTINCT
ORDER BY / GROUP BY / HAVING clause
Any WHERE clause that contains a sub query or IS NULL expression
JOIN s
A SELECT... FOR UPDATE
If you wan t to explicitly bypass the buffer, use the BYPASS BUFFER addition to the SELECT clause.
<b>Reward if useful</b> -
Buffering of the table T429i table
Hello,
system: 4.6c
The mrp jobs are getting completed beyond the schedule.We are trying to get a better executuon time for these jobs.
Wanted to know if the buffering of this table T429i will help is is faster completion of these MRPs?
Thanks.
PrasannaDear,
MRP transactions the flag to buffer the table need to set to improve the performance.
table MDBT GRPGV.
In the process overview (Transaction SM50), you can see permanent accesses to program SAPLCOIT
Reason and Prerequisites performance
Type of the planning run: Net change or regenerative planning (intensive)
Planning mode: Reactivate or reset planning dates (intensive)
Planning horizon
lead time scheduling
Technical
Database
Buffering SAP number ranges
Please refer the OSS Note 23278 - MD01, MDBT: Performance during MRP run for details. and Note 204517 - MRP: Performance problems - typical causes
Regards,
R.Brahmankar -
How to select the data efficiently from the table
hi every one,
i need some help in selecting data from FAGLFLEXA table.i have to select many amounts from different group of G/L accounts
(groups are predefined here which contains a set of g/L account no.).
if i select every time for each group then it will be a performance issue, in order to avoid it what should i do, can any one suggest me a method or a smaple query so that i can perform the task efficiently.Hi ,
1.select and keep the data in internal table
2.avoid select inside loop ..endloop.
3.try to use for all entries
check the below details
Hi Praveen,
Performance Notes
1.Keep the Result Set Small
You should aim to keep the result set small. This reduces both the amount of memory used in the database system and the network load when transferring data to the application server. To reduce the size of your result sets, use the WHERE and HAVING clauses.
Using the WHERE Clause
Whenever you access a database table, you should use a WHERE clause in the corresponding Open SQL statement. Even if a program containing a SELECT statement with no WHERE clause performs well in tests, it may slow down rapidly in your production system, where the data volume increases daily. You should only dispense with the WHERE clause in exceptional cases where you really need the entire contents of the database table every time the statement is executed.
When you use the WHERE clause, the database system optimizes the access and only transfers the required data. You should never transfer unwanted data to the application server and then filter it using ABAP statements.
Using the HAVING Clause
After selecting the required lines in the WHERE clause, the system then processes the GROUP BY clause, if one exists, and summarizes the database lines selected. The HAVING clause allows you to restrict the grouped lines, and in particular, the aggregate expressions, by applying further conditions.
Effect
If you use the WHERE and HAVING clauses correctly:
There are no more physical I/Os in the database than necessary
No unwanted data is stored in the database cache (it could otherwise displace data that is actually required)
The CPU usage of the database host is minimize
The network load is reduced, since only the data that is required by the application is transferred to the application server.
Minimize the Amount of Data Transferred
Data is transferred between the database system and the application server in blocks. Each block is up to 32 KB in size (the precise size depends on your network communication hardware). Administration information is transported in the blocks as well as the data.
To minimize the network load, you should transfer as few blocks as possible. Open SQL allows you to do this as follows:
Restrict the Number of Lines
If you only want to read a certain number of lines in a SELECT statement, use the UP TO <n> ROWS addition in the FROM clause. This tells the database system only to transfer <n> lines back to the application server. This is more efficient than transferring more lines than necessary back to the application server and then discarding them in your ABAP program.
If you expect your WHERE clause to return a large number of duplicate entries, you can use the DISTINCT addition in the SELECT clause.
Restrict the Number of Columns
You should only read the columns from a database table that you actually need in the program. To do this, list the columns in the SELECT clause. Note here that the INTO CORRESPONDING FIELDS addition in the INTO clause is only efficient with large volumes of data, otherwise the runtime required to compare the names is too great. For small amounts of data, use a list of variables in the INTO clause.
Do not use * to select all columns unless you really need them. However, if you list individual columns, you may have to adjust the program if the structure of the database table is changed in the ABAP Dictionary. If you specify the database table dynamically, you must always read all of its columns.
Use Aggregate Functions
If you only want to use data for calculations, it is often more efficient to use the aggregate functions of the SELECT clause than to read the individual entries from the database and perform the calculations in the ABAP program.
Aggregate functions allow you to find out the number of values and find the sum, average, minimum, and maximum values.
Following an aggregate expression, only its result is transferred from the database.
Data Transfer when Changing Table Lines
When you use the UPDATE statement to change lines in the table, you should use the WHERE clause to specify the relevant lines, and then SET statements to change only the required columns.
When you use a work area to overwrite table lines, too much data is often transferred. Furthermore, this method requires an extra SELECT statement to fill the work area. Minimize the Number of Data Transfers
In every Open SQL statement, data is transferred between the application server and the database system. Furthermore, the database system has to construct or reopen the appropriate administration data for each database access. You can therefore minimize the load on the network and the database system by minimizing the number of times you access the database.
Multiple Operations Instead of Single Operations
When you change data using INSERT, UPDATE, and DELETE, use internal tables instead of single entries. If you read data using SELECT, it is worth using multiple operations if you want to process the data more than once, other wise, a simple select loop is more efficient.
Avoid Repeated Access
As a rule you should read a given set of data once only in your program, and using a single access. Avoid accessing the same data more than once (for example, SELECT before an UPDATE).
Avoid Nested SELECT Loops
A simple SELECT loop is a single database access whose result is passed to the ABAP program line by line. Nested SELECT loops mean that the number of accesses in the inner loop is multiplied by the number of accesses in the outer loop. You should therefore only use nested SELECT loops if the selection in the outer loop contains very few lines.
However, using combinations of data from different database tables is more the rule than the exception in the relational data model. You can use the following techniques to avoid nested SELECT statements:
ABAP Dictionary Views
You can define joins between database tables statically and systemwide as views in the ABAP Dictionary. ABAP Dictionary views can be used by all ABAP programs. One of their advantages is that fields that are common to both tables (join fields) are only transferred once from the database to the application server.
Views in the ABAP Dictionary are implemented as inner joins. If the inner table contains no lines that correspond to lines in the outer table, no data is transferred. This is not always the desired result. For example, when you read data from a text table, you want to include lines in the selection even if the corresponding text does not exist in the required language. If you want to include all of the data from the outer table, you can program a left outer join in ABAP.
The links between the tables in the view are created and optimized by the database system. Like database tables, you can buffer views on the application server. The same buffering rules apply to views as to tables. In other words, it is most appropriate for views that you use mostly to read data. This reduces the network load and the amount of physical I/O in the database.
Joins in the FROM Clause
You can read data from more than one database table in a single SELECT statement by using inner or left outer joins in the FROM clause.
The disadvantage of using joins is that redundant data is read from the hierarchically-superior table if there is a 1:N relationship between the outer and inner tables. This can considerably increase the amount of data transferred from the database to the application server. Therefore, when you program a join, you should ensure that the SELECT clause contains a list of only the columns that you really need. Furthermore, joins bypass the table buffer and read directly from the database. For this reason, you should use an ABAP Dictionary view instead of a join if you only want to read the data.
The runtime of a join statement is heavily dependent on the database optimizer, especially when it contains more than two database tables. However, joins are nearly always quicker than using nested SELECT statements.
Subqueries in the WHERE and HAVING Clauses
Another way of accessing more than one database table in the same Open SQL statement is to use subqueries in the WHERE or HAVING clause. The data from a subquery is not transferred to the application server. Instead, it is used to evaluate conditions in the database system. This is a simple and effective way of programming complex database operations.
Using Internal Tables
It is also possible to avoid nested SELECT loops by placing the selection from the outer loop in an internal table and then running the inner selection once only using the FOR ALL ENTRIES addition. This technique stems from the time before joins were allowed in the FROM clause. On the other hand, it does prevent redundant data from being transferred from the database.
Using a Cursor to Read Data
A further method is to decouple the INTO clause from the SELECT statement by opening a cursor using OPEN CURSOR and reading data line by line using FETCH NEXT CURSOR. You must open a new cursor for each nested loop. In this case, you must ensure yourself that the correct lines are read from the database tables in the correct order. This usually requires a foreign key relationship between the database tables, and that they are sorted by the foreign key. Minimize the Search Overhead
You minimize the size of the result set by using the WHERE and HAVING clauses. To increase the efficiency of these clauses, you should formulate them to fit with the database table indexes.
Database Indexes
Indexes speed up data selection from the database. They consist of selected fields of a table, of which a copy is then made in sorted order. If you specify the index fields correctly in a condition in the WHERE or HAVING clause, the system only searches part of the index (index range scan).
The primary index is always created automatically in the R/3 System. It consists of the primary key fields of the database table. This means that for each combination of fields in the index, there is a maximum of one line in the table. This kind of index is also known as UNIQUE.
If you cannot use the primary index to determine the result set because, for example, none of the primary index fields occur in the WHERE or HAVING clause, the system searches through the entire table (full table scan). For this case, you can create secondary indexes, which can restrict the number of table entries searched to form the result set.
You specify the fields of secondary indexes using the ABAP Dictionary. You can also determine whether the index is unique or not. However, you should not create secondary indexes to cover all possible combinations of fields.
Only create one if you select data by fields that are not contained in another index, and the performance is very poor. Furthermore, you should only create secondary indexes for database tables from which you mainly read, since indexes have to be updated each time the database table is changed. As a rule, secondary indexes should not contain more than four fields, and you should not have more than five indexes for a single database table.
If a table has more than five indexes, you run the risk of the optimizer choosing the wrong one for a particular operation. For this reason, you should avoid indexes with overlapping contents.
Secondary indexes should contain columns that you use frequently in a selection, and that are as highly selective as possible. The fewer table entries that can be selected by a certain column, the higher that columns selectivity. Place the most selective fields at the beginning of the index. Your secondary index should be so selective that each index entry corresponds to at most five percent of the table entries. If this is not the case, it is not worth creating the index. You should also avoid creating indexes for fields that are not always filled, where their value is initial for most entries in the table.
If all of the columns in the SELECT clause are contained in the index, the system does not have to search the actual table data after reading from the index. If you have a SELECT clause with very few columns, you can improve performance dramatically by including these columns in a secondary index.
Formulating Conditions for Indexes
You should bear in mind the following when formulating conditions for the WHERE and HAVING clauses so that the system can use a database index and does not have to use a full table scan.
Check for Equality and Link Using AND
The database index search is particularly efficient if you check all index fields for equality (= or EQ) and link the expressions using AND.
Use Positive Conditions
The database system only supports queries that describe the result in positive terms, for example, EQ or LIKE. It does not support negative expressions like NE or NOT LIKE.
If possible, avoid using the NOT operator in the WHERE clause, because it is not supported by database indexes; invert the logical expression instead.
Using OR
The optimizer usually stops working when an OR expression occurs in the condition. This means that the columns checked using OR are not included in the index search. An exception to this are OR expressions at the outside of conditions. You should try to reformulate conditions that apply OR expressions to columns relevant to the index, for example, into an IN condition.
Using Part of the Index
If you construct an index from several columns, the system can still use it even if you only specify a few of the columns in a condition. However, in this case, the sequence of the columns in the index is important. A column can only be used in the index search if all of the columns before it in the index definition have also been specified in the condition.
Checking for Null Values
The IS NULL condition can cause problems with indexes. Some database systems do not store null values in the index structure. Consequently, this field cannot be used in the index.
Avoid Complex Conditions
Avoid complex conditions, since the statements have to be broken down into their individual components by the database system.
Reduce the Database Load
Unlike application servers and presentation servers, there is only one database server in your system. You should therefore aim to reduce the database load as much as possible. You can use the following methods:
Buffer Tables on the Application Server
You can considerably reduce the time required to access data by buffering it in the application server table buffer. Reading a single entry from table T001 can take between 8 and 600 milliseconds, while reading it from the table buffer takes 0.2 - 1 milliseconds.
Whether a table can be buffered or not depends its technical attributes in the ABAP Dictionary. There are three buffering types:
Resident buffering (100%) The first time the table is accessed, its entire contents are loaded in the table buffer.
Generic buffering In this case, you need to specify a generic key (some of the key fields) in the technical settings of the table in the ABAP Dictionary. The table contents are then divided into generic areas. When you access data with one of the generic keys, the whole generic area is loaded into the table buffer. Client-specific tables are often buffered generically by client.
Partial buffering (single entry) Only single entries are read from the database and stored in the table buffer.
When you read from buffered tables, the following happens:
1. An ABAP program requests data from a buffered table.
2. The ABAP processor interprets the Open SQL statement. If the table is defined as a buffered table in the ABAP Dictionary, the ABAP processor checks in the local buffer on the application server to see if the table (or part of it) has already been buffered.
3. If the table has not yet been buffered, the request is passed on to the database. If the data exists in the buffer, it is sent to the program.
4. The database server passes the data to the application server, which places it in the table buffer.
5. The data is passed to the program.
When you change a buffered table, the following happens:
1. The database table is changed and the buffer on the application server is updated. The database interface logs the update statement in the table DDLOG. If the system has more than one application server, the buffer on the other servers is not updated at once.
2. All application servers periodically read the contents of table DDLOG, and delete the corresponding contents from their buffers where necessary. The granularity depends on the buffering type. The table buffers in a distributed system are generally synchronized every 60 seconds (parameter: rsdisp/bufreftime).
3. Within this period, users on non-synchronized application servers will read old data. The data is not recognized as obsolete until the next buffer synchronization. The next time it is accessed, it is re-read from the database.
You should buffer the following types of tables:
Tables that are read very frequently
Tables that are changed very infrequently
Relatively small tables (few lines, few columns, or short columns)
Tables where delayed update is acceptable.
Once you have buffered a table, take care not to use any Open SQL statements that bypass the buffer.
The SELECT statement bypasses the buffer when you use any of the following:
The BYPASSING BUFFER addition in the FROM clause
The DISTINCT addition in the SELECT clause
Aggregate expressions in the SELECT clause
Joins in the FROM clause
The IS NULL condition in the WHERE clause
Subqueries in the WHERE clause
The ORDER BY clause
The GROUP BY clause
The FOR UPDATE addition
Furthermore, all Native SQL statements bypass the buffer.
Avoid Reading Data Repeatedly
If you avoid reading the same data repeatedly, you both reduce the number of database accesses and reduce the load on the database. Furthermore, a "dirty read" may occur with database tables other than Oracle. This means that the second time you read data from a database table, it may be different from the data read the first time. To ensure that the data in your program is consistent, you should read it once only and then store it in an internal table.
Sort Data in Your ABAP Programs
The ORDER BY clause in the SELECT statement is not necessarily optimized by the database system or executed with the correct index. This can result in increased runtime costs. You should only use ORDER BY if the database sort uses the same index with which the table is read. To find out which index the system uses, use SQL Trace in the ABAP Workbench Performance Trace. If the indexes are not the same, it is more efficient to read the data into an internal table or extract and sort it in the ABAP program using the SORT statement.
Use Logical Databases
SAP supplies logical databases for all applications. A logical database is an ABAP program that decouples Open SQL statements from application programs. They are optimized for the best possible database performance. However, it is important that you use the right logical database. The hierarchy of the data you want to read must reflect the structure of the logical database, otherwise, they can have a negative effect on performance. For example, if you want to read data from a table right at the bottom of the hierarchy of the logical database, it has to read at least the key fields of all tables above it in the hierarchy. In this case, it is more efficient to use a SELECT statement.
Work Processes
Work processes execute the individual dialog steps in R/3 applications. The next two sections describe firstly the structure of a work process, and secondly the different types of work process in the R/3 System.
Structure of a Work Process
Work processes execute the dialog steps of application programs. They are components of an application server. The following diagram shows the components of a work process:
Each work process contains two software processors and a database interface.
Screen Processor
In R/3 application programming, there is a difference between user interaction and processing logic. From a programming point of view, user interaction is controlled by screens. As well as the actual input mask, a screen also consists of flow logic. The screen flow logic controls a large part of the user interaction. The R/3 Basis system contains a special language for programming screen flow logic. The screen processor executes the screen flow logic. Via the dispatcher, it takes over the responsibility for communication between the work process and the SAPgui, calls modules in the flow logic, and ensures that the field contents are transferred from the screen to the flow logic.
ABAP Processor
The actual processing logic of an application program is written in ABAP - SAPs own programming language. The ABAP processor executes the processing logic of the application program, and communicates with the database interface. The screen processor tells the ABAP processor which module of the screen flow logic should be processed next. The following screen illustrates the interaction between the screen and the ABAP processors when an application program is running.
Database Interface
The database interface provides the following services:
Establishing and terminating connections between the work process and the database.
Access to database tables
Access to R/3 Repository objects (ABAP programs, screens and so on)
Access to catalog information (ABAP Dictionary)
Controlling transactions (commit and rollback handling)
Table buffer administration on the application server.
The following diagram shows the individual components of the database interface:
The diagram shows that there are two different ways of accessing databases: Open SQL and Native SQL.
Open SQL statements are a subset of Standard SQL that is fully integrated in ABAP. They allow you to access data irrespective of the database system that the R/3 installation is using. Open SQL consists of the Data Manipulation Language (DML) part of Standard SQL; in other words, it allows you to read (SELECT) and change (INSERT, UPDATE, DELETE) data. The tasks of the Data Definition Language (DDL) and Data Control Language (DCL) parts of Standard SQL are performed in the R/3 System by the ABAP Dictionary and the authorization system. These provide a unified range of functions, irrespective of database, and also contain functions beyond those offered by the various database systems.
Open SQL also goes beyond Standard SQL to provide statements that, in conjunction with other ABAP constructions, can simplify or speed up database access. It also allows you to buffer certain tables on the application server, saving excessive database access. In this case, the database interface is responsible for comparing the buffer with the database. Buffers are partly stored in the working memory of the current work process, and partly in the shared memory for all work processes on an application server. Where an R/3 System is distributed across more than one application server, the data in the various buffers is synchronized at set intervals by the buffer management. When buffering the database, you must remember that data in the buffer is not always up to date. For this reason, you should only use the buffer for data which does not often change.
Native SQL is only loosely integrated into ABAP, and allows access to all of the functions contained in the programming interface of the respective database system. Unlike Open SQL statements, Native SQL statements are not checked and converted, but instead are sent directly to the database system. Programs that use Native SQL are specific to the database system for which they were written. R/3 applications contain as little Native SQL as possible. In fact, it is only used in a few Basis components (for example, to create or change table definitions in the ABAP Dictionary).
The database-dependent layer in the diagram serves to hide the differences between database systems from the rest of the database interface. You choose the appropriate layer when you install the Basis system. Thanks to the standardization of SQL, the differences in the syntax of statements are very slight. However, the semantics and behavior of the statements have not been fully standardized, and the differences in these areas can be greater. When you use Native SQL, the function of the database-dependent layer is minimal.
Types of Work Process
Although all work processes contain the components described above, they can still be divided into different types. The type of a work process determines the kind of task for which it is responsible in the application server. It does not specify a particular set of technical attributes. The individual tasks are distributed to the work processes by the dispatcher.
Before you start your R/3 System, you determine how many work processes it will have, and what their types will be. The dispatcher starts the work processes and only assigns them tasks that correspond to their type. This means that you can distribute work process types to optimize the use of the resources on your application servers.
The following diagram shows again the structure of an application server, but this time, includes the various possible work process types:
The various work processes are described briefly below. Other parts of this documentation describe the individual components of the application server and the R/3 System in more detail.
Dialog Work Process
Dialog work processes deal with requests from an active user to execute dialog steps.
Update Work Process
Update work processes execute database update requests. Update requests are part of an SAP LUW that bundle the database operations resulting from the dialog in a database LUW for processing in the background.
Background Work Process
Background work processes process programs that can be executed without user interaction (background jobs).
Enqueue Work Process
The enqueue work process administers a lock table in the shared memory area. The lock table contains the logical database locks for the R/3 System and is an important part of the SAP LUW concept. In an R/3 System, you may only have one lock table. You may therefore also only have one application server with enqueue work processes.
Spool Work Process
The spool work process passes sequential datasets to a printer or to optical archiving. Each application server may contain several spool work process.
The services offered by an application server are determined by the types of its work processes. One application server may, of course, have more than one function. For example, it may be both a dialog server and the enqueue server, if it has several dialog work processes and an enqueue work process.
You can use the system administration functions to switch a work process between dialog and background modes while the system is still running. This allows you, for example, to switch an R/3 System between day and night operation, where you have more dialog than background work processes during the day, and the other way around during the night.
ABAP Application Server
R/3 programs run on application servers. They are an important component of the R/3 System. The following sections describe application servers in more detail.
Structure of an ABAP Application Server
The application layer of an R/3 System is made up of the application servers and the message server. Application programs in an R/3 System are run on application servers. The application servers communicate with the presentation components, the database, and also with each other, using the message server.
The following diagram shows the structure of an application server:
The individual components are:
Work Processes
An application server contains work processes, which are components that can run an application. Work processes are components that are able to execute an application (that is, one dialog step each). Each work process is linked to a memory area containing the context of the application being run. The context contains the current data for the application program. This needs to be available in each dialog step. Further information about the different types of work process is contained later on in this documentation.
Dispatcher
Each application server contains a dispatcher. The dispatcher is the link between the work processes and the users logged onto the application server. Its task is to receive requests for dialog steps from the SAP GUI and direct them to a free work process. In the same way, it directs screen output resulting from the dialog step back to the appropriate user.
Gateway
Each application server contains a gateway. This is the interface for the R/3 communication protocols (RFC, CPI/C). It can communicate with other application servers in the same R/3 System, with other R/3 Systems, with R/2 Systems, or with non-SAP systems.
The application server structure as described here aids the performance and scalability of the entire R/3 System. The fixed number of work processes and dispatching of dialog steps leads to optimal memory use, since it means that certain components and the memory areas of a work process are application-independent and reusable. The fact that the individual work processes work independently makes them suitable for a multi-processor architecture. The methods used in the dispatcher to distribute tasks to work processes are discussed more closely in the section Dispatching Dialog Steps.
Shared Memory
All of the work processes on an application server use a common main memory area called shared memory to save contexts or to buffer constant data locally.
The resources that all work processes use (such as programs and table contents) are contained in shared memory. Memory management in the R/3 System ensures that the work processes always address the correct context, that is the data relevant to the current state of the program that is running. A mapping process projects the required context for a dialog step from shared memory into the address of the relevant work process. This reduces the actual copying to a minimum.
Local buffering of data in the shared memory of the application server reduces the number of database reads required. This reduces access times for application programs considerably. For optimal use of the buffer, you can concentrate individual applications (financial accounting, logistics, human resources) into separate application server groups.
Database Connection
When you start up an R/3 System, each application server registers its work processes with the database layer, and receives a single dedicated channel for each. While the system is running, each work process is a user (client) of the database system (server). You cannot change the work process registration while the system is running. Neither can you reassign a database channel from one work process to another. For this reason, a work process can only make database changes within a single database logical unit of work (LUW). A database LUW is an inseparable sequence of database operations. This has important consequences for the programming model explained below.
Dispatching Dialog Steps
The number of users logged onto an application server is often many times greater than the number of available work processes. Furthermore, it is not restricted by the R/3 system architecture. Furthermore, each user can run several applications at once. The dispatcher has the important task of distributing all dialog steps among the work processes on the application server.
The following diagram is an example of how this might happen:
1. The dispatcher receives the request to execute a dialog step from user 1 and directs it to work process 1, which happens to be free. The work process addresses the context of the application program (in shared memory) and executes the dialog step. It then becomes free again.
2. The dispatcher receives the request to execute a dialog step from user 2 and directs it to work process 1, which is now free again. The work process executes the dialog step as in step 1.
3. While work process 1 is still working, the dispatcher receives a further request from user 1 and directs it to work process 2, which is free.
4. After work processes 1 and 2 have finished processing their dialog steps, the dispatcher receives another request from user 1 and directs it to work process 1, which is free again.
5. While work process 1 is still working, the dispatcher receives a further request from user 2 and directs it to work process 2, which is free.
From this example, we can see that:
A dialog step from a program is assigned to a single work process for execution.
The individual dialog steps of a program can be executed on different work processes, and the program context must be addressed for each new work process.
A work process can execute dialog steps of different programs from different users.
The example does not show that the dispatcher tries to distribute the requests to the work processes such that the same work process is used as often as possible for the successive dialog steps in an application. This is useful, since it saves the program context having to be addressed each time a dialog step is executed.
Dispatching and the Programming Model
The separation of application and presentation layer made it necessary to split up application programs into dialog steps. This, and the fact that dialog steps are dispatched to individual work processes, has had important consequences for the programming model.
As mentioned above, a work process can only make database changes within a single database logical unit of work (LUW). A database LUW is an inseparable sequence of database operations. The contents of the database must be consistent at its beginning and end. The beginning and end of a database LUW are defined by a commit command to the database system (database commit). During a database LUW, that is, between two database commits, the database system itself ensures consistency within the database. In other words, it takes over tasks such as locking database entries while they are being edited, or restoring the old data (rollback) if a step terminates in an error.
A typical SAP application program extends over several screens and the corresponding dialog steps. The user requests database changes on the individual screens that should lead to the database being consistent once the screens have all been processed. However, the individual dialog steps run on different work processes, and a single work process can process dialog steps from other applications. It is clear that two or more independent applications whose dialog steps happen to be processed on the same work process cannot be allowed to work with the same database LUW.
Consequently, a work process must open a separate database LUW for each dialog step. The work process sends a commit command (database commit) to the database at the end of each dialog step in which it makes database changes. These commit commands are called implicit database commits, since they are not explicitly written into the application program.
These implicit database commits mean that a database LUW can be kept open for a maximum of one dialog step. This leads to a considerable reduction in database load, serialization, and deadlocks, and enables a large number of users to use the same system.
However, the question now arises of how this method (1 dialog step = 1 database LUW) can be reconciled with the demand to make commits and rollbacks dependent on the logical flow of the application program instead of the technical distribution of dialog steps. Database update requests that depend on one another form logical units in the program that extend over more than one dialog step. The database changes associated with these logical units must be executed together and must also be able to be undone together.
The SAP programming model contains a series of bundling techniques that allow you to group database updates together in logical units. The section of an R/3 application program that bundles a set of logically-associated database operations is called an SAP LUW. Unlike a database LUW, a SAP LUW includes all of the dialog steps in a logical unit, including the database update.
Happy Reading...
shibu -
Getting the table names in an MS Access database
Hi,
I am new to JDBC and making a client/server application that updates a MS Access database through jdbc:odbc.
I need to get a list of existing user tables in the db. I have found a great document on the net which has the code, however the code doesn't work. I have tried different ways and looked every where with no success. (link to the doco: http://www-128.ibm.com/developerworks/opensource/library/j-jdbc-objects/)
Here is my dbManager class that handles all db related services in my application. I would appreciate any help I can get as I have exhusted all my avenues.
Thanks
Sep,
* dbManager.java
* Created on 31 October 2005, 10:20
* To change this template, choose Tools | Options and locate the template under
* the Source Creation and Management node. Right-click the template and choose
* Open. You can then make changes to the template in the Source Editor.
import java.io.*;
import java.sql.*;
import java.util.regex.*;
* @author AUMahdavSe
public class dbManager {
/** Constant Declaration */
public static final String Driver = "sun.jdbc.odbc.JdbcOdbcDriver";
public static final
String sqlCreateTable = "create table TABLENAME (" +
"name varchar (100)," +
"surname varchar(100)," +
"computerType integer," +
"computerNAL varchar(20)," +
"haveMonitor integer," +
"monitorNAL varchar (20)," +
"auditDate varchar(10) );";
public static final String sqlUpdateTable = "insert into TABLENAME values" +
" (NAMEHOLDER, SURNAMEHOLDER, COMPTYPE, COMPNAL, HAVEMON, MONNAL);";
/** Attributes */
private String dbURL = "jdbc:odbc:";
private String Username = "admin"; // user input
private String Password = "purina123"; // user input
private String ODBCDataSource; // config file
private String dbPath; // set through config file or defaults to current folder
private String configFile = "config.txt"; // set either at commandline or defaults to current folder
private Connection con = null;
private Statement stmt = null;
private ResultSet tables;
private DatabaseMetaData dma;
private ResultSetMetaData rsmd;
private String CurrentAuditTable = "TestTable2";
int numCols, i;
/** Set Methodes */
public void setUsername( String usr ) {
this.Username = usr;
public void setPassword( String pswd ) {
this.Password = pswd;
public void setDbPath( String path ) {
this.dbPath = path;
public void setODBCDataSource( String ds ) {
this.ODBCDataSource = ds;
public void setDbURL( String dsname ) {
this.dbURL = this.dbURL + dsname;
/** Get Methodes */
public String getDriver() {
return this.Driver;
// can be run only after a connection obj is setup
public void getMDA() {
try {
this.dma = this.con.getMetaData();
catch (SQLException ex) {
System.err.println("database connection: " + ex.getMessage());
public void getDBTables() {
//now dump out the names of the tables in the database
String[] types = new String[1];
types[0] = "TABLES"; //set table type mask
//note the %-sign is a wild card (not '*')
try {
this.tables = this.dma.getTables(null, null, "%", types);
dumpResults("--Tables--");
this.tables.close();
//this.listTables();
catch (SQLException ex) {
System.err.println("database connection: " + ex.getMessage());
// listing tables
/*int count = 0;
int numCols = 0;
//ResultSetMetaData rsmd;
try {
System.out.println("Listing db tables ...");
//this.tables.beforeFirst();
rsmd = this.tables.getMetaData();
numCols = rsmd.getColumnCount();
System.out.println("number of cols: " + numCols);
boolean more = this.tables.first();
System.out.println("this is why: " + more);
while ( more ) {
count++;
for (int i = 1; i <= numCols; i++)
System.out.print( "Table-" + count + " -> " + this.tables.getString(count)+" " );
System.out.println();
more = this.tables.next();
catch ( SQLException ex ) {
System.out.println( "problem listing db tables: " + ex.getMessage() );
/** Other Methodes */
// Initialize the db parameters, like driver, username, passwd, etc.
public void dbInitialize() {
// load configuration from config.txt (dbPath and ODBC Data Source name)
this.loadDbConfig();
// loadDriver
this.loadDriver();
// get username and password for the ODBC from user
this.getDSSecurity();
// populate dbURL, username and password
this.setDbURL( this.ODBCDataSource );
// connect to db
this.dbConnect();
// get db metadata
this.getMDA();
// get a list of tables in db
this.getDBTables();
// load JDBC driver
public void loadDriver() {
try {
Class.forName( getDriver() );
} catch (Exception e) {
System.out.println("Failed to load JDBC/ODBC driver.");
return;
// connects to db and create a Connection obj and a Statement obj
public void dbConnect() {
try {
this.con = DriverManager.getConnection (
this.dbURL,
this.Username,
this.Password);
this.stmt = con.createStatement();
} catch (Exception e) {
System.err.println("problems connecting to "+this.dbURL);
// creates table tblname in db
public void CreateTable( String tblname ) {
try {
String sqlcommand = mergeTblName(sqlCreateTable, tblname);
this.stmt.execute( sqlcommand );
catch (SQLException ex) {
System.err.println("problems with SQL statement sent to "+this.dbURL+
": "+ex.getMessage());
System.out.println("SQL Command: " + mergeTblName(sqlCreateTable, tblname) );
// updates db with new record(s) by executing the SQL query sqlstmt
// and closes db connection
public void dbUpdate( String sqlstmt ) {
try {
// execute SQL commands to create table, insert data
this.stmt.execute( sqlstmt );
this.con.close();
} catch (Exception e) {
System.err.println("problems with SQL sent to "+this.dbURL+
": "+e.getMessage());
// list all user tables in the db
public void listTables() {
//now dump out the names of the tables in the database
int count = 0;
try {
System.out.println("Listing db tables ...");
//this.tables.beforeFirst();
while ( this.tables.next() ) {
count++;
System.out.print( "Table-" + count + " -> " + this.tables.getString(1) );
System.out.println();
catch ( SQLException ex ) {
System.out.println( "problem listing db tables: " + ex.getMessage() );
// checks whether tbname exist in db as a table
// this function has to be called after dbConnect
public boolean tableExists( String tbname ) {
boolean tbexists = false;
//get the database metadata
try {
dma = con.getMetaData();
catch (SQLException ex) {
System.err.println("database connection: " + ex.getMessage());
//now dump out the names of the tables in the database
String[] types = new String[1];
types[0] = "TABLES"; //set table type mask
//note the %-sign is a wild card (not '*')
try {
tables = dma.getTables(null, null, "%", types);
catch (SQLException ex) {
System.err.println("database connection: " + ex.getMessage());
try {
while ( tables.next() ) {
if ( tbname.equalsIgnoreCase( tables.getString(1) ) ) {
tbexists = true;
catch ( SQLException ex ) {
System.err.println("database connection: " + ex.getMessage());
return tbexists;
// merge tablename using REGEX
public String mergeTblName( String sqlcommand, String tbname ) {
String REGEX = "TABLENAME";
String INPUT = sqlcommand;
String REPLACE = tbname;
Pattern p = Pattern.compile(REGEX);
Matcher m = p.matcher(INPUT); // get a matcher object
INPUT = m.replaceAll(REPLACE);
//System.out.println(INPUT);
return INPUT;
// merge feildnames specific terms using REGEX
public String mergeFldName( Message msg ) {
String sqlcommand;
sqlcommand = "insert into TABLENAME values" +
" ('" + msg.getName() + "', '" + msg.getSurname() + "', " +
msg.getComputerType() + ", '" + msg.getComputerNAL() + "', " +
msg.getHaveMonitor() + ", '" + msg.getMonitorNAL() + "', '" +
msg.getDateOfMsg() + "');";
sqlcommand = mergeTblName( sqlcommand, CurrentAuditTable );
return sqlcommand;
// get users input char
/**public char getChar() {
int i = System.in.read();
while (i != -1) {
// here's your character
char c = (char) i;
i = System.in.read();
return (char) i;
// load the config parameters from config.txt
public void loadDbConfig() {
// make a file obj pointing to the config file config.txt
File configFile = new File( this.configFile );
//...checks on configFile are elided
StringBuffer contents = new StringBuffer();
//declared here only to make visible to finally clause
BufferedReader input = null;
try {
//use buffering
//this implementation reads one line at a time
input = new BufferedReader( new FileReader(configFile) );
String line = null; //not declared within while loop
int count = 0;
while (( line = input.readLine()) != null){
//first line in config file is dbPath
if(count == 0) this.setDbPath( line.trim() );
//second line in config file is ODBCDataSource
if(count == 1) this.setODBCDataSource( line.trim() );
count++;
//contents.append(line);
//contents.append(System.getProperty("line.separator"));
catch (FileNotFoundException ex) {
System.err.println("the file congif.txt cannot be found ...");
System.err.print("Enter the path to db file (e.g. c:\\temp): ");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
// read the db path from the command-line; need to use try/catch with the
// readLine() method
try {
this.setDbPath( br.readLine() );
catch (IOException ioe) {
System.out.println("IO error trying to read user input.");
System.exit(1);
System.err.print("Enter the name of the ODBC Data Source: ");
// read the ODBC Data Source name from the command-line; need to use try/catch with the
// readLine() method
try {
this.setODBCDataSource( br.readLine() );
catch (IOException ioe) {
System.out.println("IO error trying to read user input.");
System.exit(1);
ex.printStackTrace();
catch (IOException ex){
//ex.printStackTrace();
finally {
try {
if (input!= null) {
//flush and close both "input" and its underlying FileReader
input.close();
catch (IOException ex) {
//ex.printStackTrace();
//return contents.toString();
// get datasource security details i.e. username and password
public void getDSSecurity() {
// get username
System.out.print("Enter username for the ODBC DataSource: ");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
// read the username from the command-line; need to use try/catch with the
// readLine() method
try {
this.setUsername( br.readLine() );
catch (IOException ioe) {
System.out.println("IO error trying to read username.");
System.exit(1);
// get password
System.out.print("Enter password: ");
// read the username from the command-line; need to use try/catch with the
// readLine() method
try {
this.setPassword( br.readLine() );
catch (IOException ioe) {
System.out.println("IO error trying to read password.");
System.exit(1);
private void dumpResults(String head)
//this is a general routine to print out
//column headers and the contents of each column
System.out.println(head);
try
//get the number of columns from the metadata
this.rsmd = this.tables.getMetaData();
numCols = this.rsmd.getColumnCount();
//print out the column names
for (i = 1; i<= numCols; i++)
System.out.print(rsmd.getColumnName(i)+" ");
System.out.println();
//print out the column contents
boolean more = this.tables.next();
while (more)
for (i = 1; i <= numCols; i++)
System.out.print(this.tables.getString(i)+" ");
System.out.println();
more = this.tables.next();
catch(Exception e)
{System.out.println(e.getMessage());}
/** Creates a new instance of dbManager */
public dbManager() {
this.dbInitialize();
}here is the result when I make a new dbManager obj from my server class which is a multithreaded one.
H:\java>java EchoServer
Enter username for the ODBC DataSource: admin
Enter password: purina123
Tables
TABLE_CAT TABLE_SCHEM TABLE_NAME TABLE_TYPE REMARKS
Listening for clients on 12111...
here is the code of my server class called EchoServer:
import java.net.*;
import java.io.*;
public class EchoServer
ServerSocket m_ServerSocket;
dbManager haDB;
public EchoServer()
// db methods to setup a jdbc connection to the database
haDB = new dbManager();
// list tables
//haDB.listTables();
//haDB.getDBTables();
// create table
//haDB.CreateTable("TestTable2");
// update table
// server code
try
// Create the server socket.
m_ServerSocket = new ServerSocket(12111);
catch(IOException ioe)
System.out.println("Could not create server socket at 12111. Quitting.");
System.exit(-1);
System.out.println("Listening for clients on 12111...");
// Successfully created Server Socket. Now wait for connections.
int id = 0;
while(true)
try
// Accept incoming connections.
Socket clientSocket = m_ServerSocket.accept();
// accept() will block until a client connects to the server.
// If execution reaches this point, then it means that a client
// socket has been accepted.
// For each client, we will start a service thread to
// service the client requests. This is to demonstrate a
// multithreaded server, although not required for such a
// trivial application. Starting a thread also lets our
// EchoServer accept multiple connections simultaneously.
// Start a service thread
ClientServiceThread cliThread = new ClientServiceThread(clientSocket, id++, haDB);
cliThread.start();
catch(IOException ioe)
System.out.println("Exception encountered on accept. Ignoring. Stack Trace :");
ioe.printStackTrace();
public static void main (String[] args)
new EchoServer();
class ClientServiceThread extends Thread
Socket m_clientSocket;
int m_clientID = -1;
dbManager m_db;
boolean m_bRunThread = true;
ClientServiceThread(Socket s, int clientID, dbManager db)
m_clientSocket = s;
m_clientID = clientID;
m_db = db;
public void run()
// Obtain the input stream and the output stream for the socket
// A good practice is to encapsulate them with a BufferedReader
// and a PrintWriter as shown below.
BufferedReader in = null;
PrintWriter out = null;
Message msg = new Message();
// Print out details of this connection
System.out.println("Accepted Client : ID - " + m_clientID + " : Address - " +
m_clientSocket.getInetAddress().getHostName());
try
in = new BufferedReader(new InputStreamReader(m_clientSocket.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(m_clientSocket.getOutputStream()));
// At this point, we can read for input and reply with appropriate output.
// Run in a loop until m_bRunThread is set to false
while(m_bRunThread)
// read incoming stream
String clientCommand = in.readLine();
if ( clientCommand.indexOf(",") != -1 ) {
msg.deserialize( clientCommand );
System.out.println("SQL command: " + m_db.mergeFldName(msg) );
m_db.dbUpdate( m_db.mergeFldName(msg) );
//System.out.println("Name :" + msg.getName() );
//System.out.println("Surname :" + msg.getSurname() );
//System.out.println("ComputerType :" + msg.getComputerType() );
//System.out.println("ComputerNAL :" + msg.getComputerNAL() );
//System.out.println("HaveMonitor :" + msg.getHaveMonitor() );
//System.out.println("Monitor NAL :" + msg.getMonitorNAL() );
//System.out.println("AuditDate :" + msg.getDateOfMsg() );
System.out.println("Client Says :" + clientCommand);
if(clientCommand.equalsIgnoreCase("quit"))
// Special command. Quit this thread
m_bRunThread = false;
System.out.print("Stopping client thread for client : " + m_clientID);
else
// Echo it back to the client.
out.println(clientCommand);
out.flush();
catch(Exception e)
e.printStackTrace();
finally
// Clean up
try
in.close();
out.close();
m_clientSocket.close();
System.out.println("...Stopped");
catch(IOException ioe)
ioe.printStackTrace();
}I find that taking any problem and reducing it to the simplest thing is the best way to approach it.
Why you had to post all that bloody code (especially since you didn't write it) is beyond me.
This will list all the tables in an Access database (or any other, for that matter):
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import org.jdom.Element;
import org.jdom.Document;
import org.jdom.output.XMLOutputter;
public class TableLister
public static final String DRIVER = "sun.jdbc.odbc.JdbcOdbcDriver";
public static final String DATABASE = "jdbc:odbc:DRIVER={Microsoft Access Driver (*.mdb)};DBQ=c:\\Edu\\Java\\Forum\\DataConnection.mdb";
public static final String USERNAME = "admin";
public static final String PASSWORD = "";
public static void main(String [] args)
try
String driver = ((args.length > 0) ? args[0] : DRIVER);
String url = ((args.length > 1) ? args[1] : DATABASE);
String username = ((args.length > 2) ? args[2] : USERNAME);
String password = ((args.length > 3) ? args[3] : PASSWORD);
Class.forName(driver);
Connection conn = DriverManager.getConnection(url, username, password);
DatabaseMetaData meta = conn.getMetaData();
// Bring back ALL tables and views, including SYSTEM tables.
ResultSet tables = meta.getTables(null, null, null, null);
ResultSetMetaData rsmd = tables.getMetaData();
int numColumns = rsmd.getColumnCount();
List columnNames = new ArrayList();
for (int j = 0; j < numColumns; ++j)
columnNames.add(rsmd.getColumnName(j+1));
Element root = new Element("tables");
int tableCount = 0;
while (tables.next())
Element table = new Element("table");
table.setAttribute("id", Integer.toString(++tableCount));
for (int j = 0; j < numColumns; ++j)
Element column = new Element((String)columnNames.get(j));
column.setText(tables.getString((String)columnNames.get(j)));
table.addContent(column);
root.addContent(table);
conn.close();
Document doc = new Document(root);
XMLOutputter outputter = new XMLOutputter(" ", true);
System.out.println(outputter.outputString(doc));
catch (ClassNotFoundException e)
System.err.println("Couldn't load JDBC driver class");
e.printStackTrace();
catch (SQLException e)
System.err.println("SQL state: " + e.getSQLState());
System.err.println("SQL error: " + e.getErrorCode());
e.printStackTrace();
catch (Exception e)
e.printStackTrace();
}Run it and see if it works for you. If it does, put the essence of the code into your stuff.
% -
Hi,
I thought of putting my question in the forum. The question is, when we are doing some changes in the forms applications in oracle apps and save the data, is there anyway that i can know to how many and which tables the data is getting saved to?? Because, in OAFramework, its simple as the goes to the VO and we can check the VO query to know the tables but what about the forms??
I know the Examine feature but is there any other way to find the exacty tables where the data is going to get saved??
Thanks and have a nice weekend.Prasanna, I checked. To explain you in brief, i changed some phone number and preferred name values in a new custom page i created and i also enabled the trace before making changes to the data.
Now when i checked the file i see the below information but i don't see any information related to the phone numbers,per_phones or per_all_people_f tables.
TKPROF: Release 8.0.6.3.0 - Production on Mon Apr 13 14:02:58 2009
(c) Copyright 1999 Oracle Corporation. All rights reserved.
Trace file: /home/pkotharu/ts01_ora_1761462_MSALAH.trc
Sort options: default
count = number of times OCI procedure was executed
cpu = cpu time in seconds executing
elapsed = elapsed time in seconds executing
disk = number of physical reads of buffers from disk
query = number of buffers gotten for consistent read
current = number of buffers gotten in current mode (usually for update)
rows = number of rows processed by the fetch or execute call
alter session set events='10046 trace name context forever, level 1'
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 3 0.00 2.48 0 0 0 0
Fetch 0 0.00 0.00 0 0 0 0
total 3 0.00 2.48 0 0 0 0
Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS) (recursive depth: 1)
BEGIN fnd_trace.start_trace(:1); END;
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 3 100.00 78.42 0 0 0 3
Fetch 0 0.00 0.00 0 0 0 0
total 3 100.00 78.42 0 0 0 3
Misses in library cache during parse: 0
Misses in library cache during execute: 3
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS)
BEGIN fnd_trace.stop_trace(:1); END;
call count cpu elapsed disk query current rows
Parse 1 0.00 4.10 0 0 0 0
Execute 3 0.00 43.40 0 0 0 3
Fetch 0 0.00 0.00 0 0 0 0
total 4 0.00 47.50 0 0 0 3
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS)
ALTER SESSION SET SQL_TRACE=FALSE
call count cpu elapsed disk query current rows
Parse 3 0.00 1.75 0 0 0 0
Execute 3 0.00 2.39 0 0 0 0
Fetch 0 0.00 0.00 0 0 0 0
total 6 0.00 4.14 0 0 0 0
Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS) (recursive depth: 1)
select spid
from
v$process where addr in (select paddr from v$session where audsid =
userenv('sessionid'))
call count cpu elapsed disk query current rows
Parse 3 0.00 47.60 0 0 0 0
Execute 3 0.00 0.74 0 0 0 0
Fetch 3 0.00 112.12 0 0 0 3
total 9 0.00 160.46 0 0 0 3
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS)
Rows Row Source Operation
1 MERGE JOIN
148 FIXED TABLE FULL X$KSUPR
1 SORT JOIN
1 VIEW
1 SORT UNIQUE
1 FIXED TABLE FULL X$KSUSE
error during parse of EXPLAIN PLAN statement
ORA-01039: insufficient privileges on underlying objects of the view
parse error offset: 88
SELECT VALUE
FROM
ICX_SESSION_ATTRIBUTES WHERE SESSION_ID = :B2 AND NAME = :B1
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 4 0.00 1.00 0 0 0 0
Fetch 4 0.00 0.59 0 12 0 0
total 8 0.00 1.59 0 12 0 0
Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS) (recursive depth: 1)
Rows Execution Plan
0 SELECT STATEMENT GOAL: CHOOSE
0 TABLE ACCESS GOAL: ANALYZED (BY INDEX ROWID) OF
'ICX_SESSION_ATTRIBUTES'
0 INDEX GOAL: ANALYZED (UNIQUE SCAN) OF
'ICX_SESSION_ATTRIBUTES_U1' (UNIQUE)
declare val varchar2(256);begin :1 :=
fnd_session_management.GETSESSIONATTRIBUTEVALUE(:2,:3);end;
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 4 100.00 53.14 0 0 0 4
Fetch 0 0.00 0.00 0 0 0 0
total 4 100.00 53.14 0 0 0 4
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS)
SELECT USER_ID, RESPONSIBILITY_ID, RESPONSIBILITY_APPLICATION_ID, ORG_ID,
FUNCTION_ID,DATE_FORMAT_MASK, LANGUAGE_CODE, NLS_LANGUAGE,
NLS_DATE_LANGUAGE, NLS_NUMERIC_CHARACTERS, NLS_SORT, NLS_TERRITORY,
SECURITY_GROUP_ID, LOGIN_ID
FROM
ICX_SESSIONS WHERE XSID=:1
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 1 0.00 0.43 0 0 0 0
Fetch 1 0.00 0.44 0 4 0 1
total 2 0.00 0.87 0 4 0 1
Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS)
Rows Execution Plan
0 SELECT STATEMENT GOAL: CHOOSE
0 TABLE ACCESS GOAL: ANALYZED (BY INDEX ROWID) OF
'ICX_SESSIONS'
0 INDEX GOAL: ANALYZED (UNIQUE SCAN) OF 'ICX_SESSIONS_U2'
(UNIQUE)
SELECT SESSION_ID
FROM
ICX_SESSIONS WHERE XSID = :B1
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 1 0.00 0.27 0 0 0 0
Fetch 1 0.00 0.20 0 4 0 1
total 2 0.00 0.47 0 4 0 1
Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS) (recursive depth: 1)
Rows Execution Plan
0 SELECT STATEMENT GOAL: CHOOSE
0 TABLE ACCESS GOAL: ANALYZED (BY INDEX ROWID) OF
'ICX_SESSIONS'
0 INDEX GOAL: ANALYZED (UNIQUE SCAN) OF 'ICX_SESSIONS_U2'
(UNIQUE)
begin :1 := fnd_session_utilities.XSID_to_SessionID(:2);end;
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 1 0.00 51.58 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
total 1 0.00 51.58 0 0 0 1
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer goal: CHOOSE
Parsing user id: 181 (APPS)
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 4 0.00 51.70 0 0 0 0
Execute 15 200.00 227.71 0 0 0 11
Fetch 4 0.00 112.56 0 4 0 4
total 23 200.00 391.97 0 4 0 15
Misses in library cache during parse: 2
Misses in library cache during execute: 5
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 5 0.00 2.27 0 0 0 0
Execute 13 0.00 6.52 0 0 0 0
Fetch 7 0.00 1.16 0 20 0 3
total 25 0.00 9.95 0 20 0 3
Misses in library cache during parse: 0
16 user SQL statements in session.
2 internal SQL statements in session.
18 SQL statements in session.
3 statements EXPLAINed in this session.
Trace file: /home/pkotharu/ts01_ora_1761462_MSALAH.trc
Trace file compatibility: 7.03.02
Sort options: default
1 session in tracefile.
16 user SQL statements in trace file.
2 internal SQL statements in trace file.
18 SQL statements in trace file.
11 unique SQL statements in trace file.
3 SQL statements EXPLAINed using schema:
APPS.prof$plan_table
Default table was used.
Table was created.
Table was dropped.
178 lines in trace file. -
We are trying to boost the performance of a table join in a custom program. I created a table view to see if the performance was any better than coding the join in the program. It was not really any better. Then, I played around with the table buffering a bit. When I set the table buffering to Generic with 3 fields, the program ran over 50% faster. Is it a bad thing to turn on the buffer for a table view? The tables joined are MKPF and MSEG.
Hi Kenneth,
I don't know in what kind of company you are working, but the table you are referring to will normally be updated very regularly (material documents). In that case it doesn't make too much sense to turn on buffering as the buffer will be invalidated and refreshed very often.
Perhaps creating a suitable index will be more efficient?
Regards,
John. -
Reading and Updating the table at the same time
Hi all
I need to read from a table to check whether a record exist in there or not, then if not add the record to the table (in the same dataflow). Is there any way to use a table as a source and as a target at the same time?
While I'm doing this procedure, I don't want to add a record that I had inserted before twice (I need to get the latest veriosn of the table when I'm working with that). For example, in the same process, when I check the table and the record was not there, I insert the record, I read the table again , if this time again I want to read the same record that I had inserted just before, does DS distingish that, or all records will be comitted based on the commit size which is by default 1000?
I can not change the commit size to 1 to tell DS to commit record by record, as I have turned on the transactional load and the commit size is disabled for me.
Do you have any experience about my problem?
Any help is greatly appreciated.You need two dataflows. A first that reads your source and inserts/updates the lookup table. And then you read your source again and use the now current lookup table.
Even if you would set the commit rate to 1 it would not help as there are so many buffers between the transforms. What you would require is that only one row is in the dataflow at any given time - and that would take ages. -
What is the table and purpose?
let me know what is the table and its contents and purpose....i wil be thanks to you if i get answers
Table is a data repository in which all the master data and transactional data gets stored. All components/ data of SAP stored in Tables.
<b>SAP Table Types</b>
I. Transparent tables (BKPF, VBAK, VBAP, KNA1, COEP)
Allows secondary indexes (SE11->Display Table->Indexes)
Can be buffered (SE11->Display Table->technical settings) Heavily updated tables should not be buffered.
<b>II. Pool Tables (match codes, look up tables)</b>
Should be accessed via primary key or
Should be buffered (SE11->Display Table->technical settings)
No secondary indexes
Select * is Ok because all columns retrieved anyway
<b>III. Cluster Tables (BSEG,BSEC)</b>
Should be accessed via primary key - very fast retrieval otherwise very slow
No secondary indexes
Select * is Ok because all columns retrieved anyway. Performing an operation on multiple rows is more efficient than single row operations. Therefore you still want to select into an internal table. If many rows are being selected into the internal table, you might still like to retrieve specific columns to cut down on the memory required.
Statistical SQL functions (SUM, AVG, MIN, MAX, etc) not supported
Can not be buffered
<b>IV. Buffered Tables (includes both Transparent & Pool Tables)</b>
While buffering database tables in program memory (SELECT into internal table) is generally a good idea for performance, it is not always necessary. Some tables are already buffered in memory. These are mostly configuration tables. If a table is already buffered, then a select statement against it is very fast. To determine if a table is buffered, choose the 'technical settings' soft button from the data dictionary display of a table (SE12). Pool tables should all be buffered.
to know about structure. Please refer the link
http://help.sap.com/saphelp_nw2004s/helpdata/en/90/8d72fbb1af11d194f600a0c929b3c3/frameset.htm
Regards
Vivek
<b>Reward points for the useful answers</b> -
Is there good way to buffer a table in memory. We have a control table which is accessed by many transactions. So indtead of reading from the transparent table, we want 2 buffer it such that all applications can read from it.. Is there a good way to do it?
Hi Friend,
To buffer a table do following -
>>
Goto Technical settings of the table , Click on change mode, then
Click on Buffering Switched ON and choose appropriate form of buffering u require
from ---
Single Record Buffering.
Generic area buffering.
Fully Buffered .
and click on save.
I will let u know about these 3 kinds of Buffering so that u can make idea which one u want to use----
The buffering type determines which records of the table are loaded into the
buffer of the application server when a record of the table is accessed. There are
the following buffering types:
Full buffering: When a record of the table is accessed, all the records of
the table are loaded into the buffer.
Generic buffering: When a record of the table is accessed, all the records
whose left-justified part of the key is the same are loaded into the buffer.
Single-record buffering: Only the record that was accessed is loaded
into the buffer.
Hope this resolves ur issue,
Akash Rana -
Need of buffering in table creation.
what is need of buffering in table creation and data class and delivey class
Definition
The name table (nametab) contains the table and field definitions that are activated in the SAP System. An entry is made in the Repository buffer when a mass activator or a user (using the ABAP Dictionary, Transaction SE11) requests to activate a table. The corresponding name table is then generated from the information that is managed in the Repository.
The Repository buffer is mainly known as the nametab buffer (NTAB), but it is also known as the ABAP Dictionary buffer
The description of a table in the Repository is distributed among several tables (for field definition, data element definition and domain definition). This information is summarized in the name table. The name table is saved in the following database tables:
DDNTT (table definitions)
DDNTF (field descriptions)
The Repository buffer consists of four buffers in shared memory, one for each of the following:
Table definitions TTAB buffer Table DDNTT
Field descriptions FTAB buffer Table DDNTF
Initial record layouts IREC buffer Contains the record layout initialized depending on the field type
There are two kinds of table buffers:
Partial table buffers
Generic table buffers
Check this link for more details.
http://www.abapprogramming.blogspot.com/2007/11/buffering-in-sap-abap.html
Regards, -
Can any body tell me when we do full buffering db tables
hello all
can any body tell me when we do full buffering , what changes will occurs in database server?
After buffer we added some fields in database table what changes will be there in database server?Hi Swamy,
refer this link
http://help.sap.com/saphelp_47x200/helpdata/en/cf/21f244446011d189700000e8322d00/content.htm
http://help.sap.com/saphelp_47x200/helpdata/en/3d/935324d37011d194ba00a0c94260a5/content.htm
http://abapprogramming.blogspot.com/2007/11/buffering-in-sap-abap.html
Table Buffer:Table Buffer is a place on the RAM where we store the whole table temperorly.Single Buffer:It is one type of buffering techniques through which we can store single record of a table on RAM temperorly. If more details are present ...
This r some think to buffer the data in application server. Buffer not allowed will buffer data in AS. Data will be fetched directly from Database server. Buffer switched on means it buffers data in AP means data is fetched from application Server. Buffer switched allowed but switched off. Full buffer to store the table in AP. Generic buffer - It is a comparison of fields i.e. data retired by the matching record.
Cheers
Mohinder Singh Chauhan -
In oracle,
Is there any way we can buffer the tables to reduce the disk I/0 ?
If I can buffer, how big the table should I be buffering ?
I was just monitoring the top sql and some of the sql statements
have been fetching only 1000 rows but my buffer gets is around
564018250 and diskreads is 5316884.
I believe that is too much for the 1000 rows.
Can anyone please suggest me or guide me in right direction ?
From,
Pranav ThakerHi,
Yes you can create/modify table so they stay in memory once loaded.
In order to do so, you must
. have defined a Keep Cache in your S.G.A. (cf parameter DB_KEEP_CACHE_SIZE)
. tell that objects (table/index) are going to be loaded in this cache
Modifying the Keep Cache size (Default 0) might need a bounce (because of SGA_MAX_SIZE)
Modifying the objects can be achieved viaALTER TABLE table_name STORAGE (BUFFER_POOL KEEP);Before applying this method, you should read the Tuning Documentation on specialized Buffer Cache.
Furthermore, I'm not sure that it's what you should do. Maybe you should first start by tuning your SQL queries? Have a detailed look at those queries' explain plan.
Regards,
Yoann. -
ADF Desktop Integration : How to delete the table in Excel?
Hi,
I am using Jdev 11.1.1.3.0 and Excel 2007 for Oracle ADF DI, I had created an ADF table using pageDef file in the excel. Now I wanted to delete that table and use a different pageDef file.
I could not find a way to delete that table.
I deleted full row of tables and then I used different pageDef file and created a new adf table. But when I am running this version of excel, I am getting runtime exception and excel is getting corrupted.
My question how to delete the table not corrupting the Excel.
Thanks
PavanPavan,,
Welcome to OTN.
You can delete the table by selecting the top left column (of the table) and then select delete from the ADFdi tab.
Refer the documentation for more info.
http://docs.oracle.com/cd/E17904_01/web.1111/e10139/get_start_dev_tools.htm#ADFDI608
-Arun -
How can we remove the scroll bars from the table?
Hi,
I have a dynamic table. Currently the table appears with the scroll bars. But there is a requirement that the scroll bar should not appear and the table should stretch in the entire page. How can this be achieved.
Thanks in advance
NitaThanks Mohammad for the reply.
Was able to remove the scroll bars by using only the styleClass as AFStretchWidth. But there is a default partition in middle of the page still? Can i remove that too by any way.
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