Regarding buffering in techanical attributes of the table

hi experts,
cud u plz explain me these things but in your words,,,,,
BUFFERING::
1.buffering lot allowed.
2,buffering allowed but switched off.
3.buffering switched on
thnx in advance:::

Hi
Everytime there is no need for the system to fetch the data from the database tables
During runtime it creates some temporary memory like thing and keeps that fecthed records in a Buffer like thing and next time when you try to fetch the data at run time first it checks for the run time buffer is there or not, if it is there it takes the data from that buffer, instead of bring from database
see the concepts of buffering
We have 3 types of buffering
There are the following types of buffering:
o single-record buffering
o generic area buffering
o full buffering
Single-record buffering should be selected when :
o For large tables where there are frequent single-record accesses (using SELECT SINGLE ...). The size of the records being accessed should be between 100-200 KB.
o For comparatively small tables for which the access range is large, it is normally advisable to opt for full buffering. Only one database access is required to load such a table for full buffering,
while single-record buffering calls for a very large number of table accesses.
And also check this matter.
Single-record buffering: Only the records of a table that are really accessed are loaded into the buffer
Single-record buffering should be used particularly for large tables where only a few records are accessed with SELECT SINGLE. The size of the records being accessed should be between 100 and 200 KB.
Full buffering is usually more suitable for smaller tables that are accessed frequently. This is because only one database access is necessary to load such a table with full buffering, whereas several database accesses are necessary for single-record buffering.
Check this link :
http://help.sap.com/saphelp_nw04/helpdata/en/f7/e4c5a8a84a11d194eb00a0c929b3c3/content.htm

Reward points
Regards

Similar Messages

Regarding techanical attributes in the data base tables

hi gurus,
 cud u plz let me know what will happen if i select buffering not allowed and in buffering type i selected single record buffering,,is it going to work...thnx in advance......pl;z reply in your words dont copy and paste it form sap library........

These are the Technical Settings of database table and not Technical Attributes.
Technical Attributes implies, DATATYPE, SIZE etc....
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.
Regards,
Pavan

Not able to change the name of the attribute of the Table operator.

We are trying to create OMB scripts to automate certain tasks. As a part of this, there is a requirement to change the attribute name of table operators (which by default gets the name of the column). It is possible to change the attribute name from the GUI. But I was not able to do the same using OMB Scripting. Here is the script I used.
OMBALTER MAPPING 'TEST' \
MODIFY ATTRIBUTE 'GEOGRAPHY_ID' OF GROUP 'INOUTGRP1' OF OPERATOR 'TEST' \
SET PROPERTIES(BUSINESS_NAME,PRECISION,DESCRIPTION) \
VALUES('MEMBER_ID',2,'MEMBER')
This script was to change the name of the attribute - GEOGRAPHY_ID of the table operator TEST.
From what I can make out from the Scripting reference, changing BUSINESS_NAME of the attribute should do the trick but it is not happening. The syntax looks correct as the precision of the column changes.
Am I missing something? Or is it a limitation or a bug?
I use OWB client 10.2.0.1.25 and OWB repository 10.2.0.1.0.

Hi!
I'm using successfully
OMBALTER MAPPING '$mapName' MODIFY ATTRIBUTE '$attrName' OF GROUP '$groupName' OF OPERATOR '$joinName' RENAME TO '$newName'
Regards,
Carsten.

How do I use the value of a table attribute outside the table?

I have two tables that are master detail. But it might not be so obvious to the user before he knows how the page works that they are master detail. The tables are in separate showDetailItems in a panelAccordion and what I was thinking of was to show the value of one coloum in the selected row in the master in the text in the showdetail item that contains the detail table. But I can´t find the right expression to put into the accordion. How should the expression look like to get the value of an attribute in a table for use outside the table?

Thanks for the suggestion but it doesn´t work. The first problem is that the page turns blank when I use that expression for the text in the showDetailItem and the second problem is that I don´t seem to be able to use the master table as a partial trigger. When I click edit in the partial trigger property I can´t shuttle the master table over to be a partial trigger to the showDetailItem even if the table has an id.
Edited by: Atlantic Viking on Apr 2, 2009 6:24 AM
Well I figured out how to come half way. I did the following things:
1) Created an attribute value binding to the attribute I wanted to be shown in the showDetailItem
2) Set the text property in the showDetailItem to this attribute value like this #{binding.attributeValue}
To solve the problem I had with the partial triggers I continued like this
3) Gave other components on the path from the showDetailItem to the master table id´s
4) Clicked edit on the partial trigger property on the showDetailItem and was now able to shuttle the master table over to be a partial trigger.
But I now got an other problem which looks like a bug. At first when I enter the page it looks fine but when I change focus in the master table to another row part of the showDetailItem containing the detail table disapears. The detail table still remains and works as it should but the part containing the text I tried to set above disapears and the text in the showDetailItem containing the master gets replaced by the text that was supposed to be in the showDetailItem containing the detail table. Any suggestions how to correct this are very welcome.
Edited by: Atlantic Viking on Apr 2, 2009 6:59 AM

Updating an attribute of the table

Hi.,
I am using jdev11.1.5
My scenario is:
=>i had created a adf table [hd:table name
=> If the user selects the first row and after clicking the post button an attribute in [ln] table should get updated
can anyone pls tell me how to acheive this concepts
Edited by: Kristo on Sep 19, 2011 4:36 AM

sry .., i think i am not clear with my concept
I had designed a af:Table using the table name HD
If the user clicks any of the row and after clicking my post button a particular field must be updated at back end

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

Creating a Mat View having the same name with that of the table name

Hi everyone,
After dropping the mat view name "QQ.TRDLN_DIM_MV", I'm trying to re-create it by having the same name as that of the table but I got an error stating that "name is already used by an existing object". How can create a mat view to look like the object owned by schema "GQ", having a name that is the same as that of the table name, without dropping the table?
OWNER_O OBJECT_TYPE CREATED LAST_DDL_ TIMESTAMP STATUS OBJECT_NAME
===
GQ MATERIALIZED VIEW 05-NOV-08 13-DEC-08 2008-11-05:06:31:46 VALID TRDLN_DIM_MV
GQ TABLE 05-NOV-08 15-DEC-08 2008-11-05:06:31:00 VALID TRDLN_DIM_MV
QQ TABLE 17-AUG-07 16-MAR-09 2007-08-17:17:05:21 VALID TRDLN_DIM_MV
SQL>CREATE MATERIALIZED VIEW QQ.TRDLN_DIM_MV
2 TABLESPACE FPLC01S
3 NOCACHE
4 NOLOGGING
5 COMPRESS
6 PARALLEL ( DEGREE 2 INSTANCES 1 )
7 BUILD IMMEDIATE
8 REFRESH FORCE ON DEMAND
9 WITH PRIMARY KEY
10 AS
11 select /*+ NO_REWRITE */ trdln_id,
12 trdln_skid,
13 trdln_end_date,
14 first_value(trdln_end_date) over (partition by trdln_id order by trdln_end_date DESC) as MaxDate
15 from QQ.trdln_dim;
from QQ.trdln_dim
ERROR at line 15:
ORA-00955: name is already used by an existing object
I appreciate your help. Many thanks in advance!
Regards,
Radic

You'd have to rename the table (using ALTER TABLE tablename RENAME TO othername; ) before you create the MV.
You can't have both existing with the same name in the same schema.
What you see in the GQ schema is that the "table" is the underlying table for the Materialized View.
When you do a CREATE MATERIALIZED VIEW MY_MV AS ...
Oracle creates two objects with the same name, one being the Materialized View MY_MV and the other being the table MY_MV which is the physical storage. {Remember that a Materialized View is a means of getting a physical representation of a View}.
In the QQ schema what you have is either
a. a real Table
or
b. an improperly dropped MV, resulting in the underlying Table still present.

Performance issue in the table

Hi All
i have one table which is based on a VO. This VO has 150 attributes.I am facing performance issue.
first Q is i need to display only 15 attributes in the table. but other attributes are also required .
so i have two options .
1. make other as form value
or
2. make them messagetextinput and set rendered false.
i just wanted to know which will perform better.
pls help

these attributes have some default values.
i need to pass these values to the api on some action
if i dont keep in my page then
will row.getAttribute("XYZ") still carry its value
??

Banding attribute in data table not working

Hi all,
I am using the table for displaying rows of data from the backing bean. I set the banding attribute to be "row" and the bandingInterval="1",but I don't see the effect of these attributes when the table is rendered. Anything I miss in the backing bean? In case I can't make this work, I would want to fall back to drawing row and column grids in the table, similar to the "rule" attribute in the basic jsf dataTable, how do achieve the same thing with ADF table?
Thank you,
Lngo

Hi,
Can you try by casting row with PoRequisitionLinesVORowImpl.
Something like below
PoRequisitionLinesVOImpl xxReqLineVO = am.getPoRequisitionLinesVO();
PoRequisitionLinesVORowImpl xxReqLineRow = null;
 for(xxReqLineRow = (PoRequisitionLinesVORowImpl)xxReqLineVO.first(); xxReqLineRow != null; xxReqLineRow = (PoRequisitionLinesVORowImpl)xxReqLineVO.next())
 try
 String xxdelToLocId = xxReqLineRow.getDeliverToLocationId().toString());
 if(<your condition >)
 xxReqLineRow.setAttribute1("");
 else
 xxReqLineRow.setAttribute1("xx_YOUR_VALUE");
 catch(Exception e)
 throw OAException.wrapperException(e);
 xxReqLineVO.reset();
 }Thanks,
Jit

How to get the size of the table

Hi All,
How to get the size of the table in Oracle 10g?
Is there any script which needs to be run?
Regards,
Apoorv

Hi All,
Sorry but somehow the table user_segments is not populated in my case. But we have another table SYS.ALL_TABLES whose structure is given below. Would I be able to calculate the table size based on the columns given below:
ColumnName     Data Type
OWNER     VARCHAR2 (30 Byte)
TABLE_NAME     VARCHAR2 (30 Byte)
TABLESPACE_NAME     VARCHAR2 (30 Byte)
CLUSTER_NAME     VARCHAR2 (30 Byte)
IOT_NAME     VARCHAR2 (30 Byte)
STATUS     VARCHAR2 (8 Byte)
PCT_FREE     NUMBER
PCT_USED     NUMBER
INI_TRANS     NUMBER
MAX_TRANS     NUMBER
INITIAL_EXTENT     NUMBER
NEXT_EXTENT     NUMBER
MIN_EXTENTS     NUMBER
MAX_EXTENTS     NUMBER
PCT_INCREASE     NUMBER
FREELISTS     NUMBER
FREELIST_GROUPS     NUMBER
LOGGING     VARCHAR2 (3 Byte)
BACKED_UP     VARCHAR2 (1 Byte)
NUM_ROWS     NUMBER
BLOCKS     NUMBER
EMPTY_BLOCKS     NUMBER
AVG_SPACE     NUMBER
CHAIN_CNT     NUMBER
AVG_ROW_LEN     NUMBER
AVG_SPACE_FREELIST_BLOCKS     NUMBER
NUM_FREELIST_BLOCKS     NUMBER
DEGREE     VARCHAR2 (10 Byte)
INSTANCES     VARCHAR2 (10 Byte)
CACHE     VARCHAR2 (5 Byte)
TABLE_LOCK     VARCHAR2 (8 Byte)
SAMPLE_SIZE     NUMBER
LAST_ANALYZED     DATE
PARTITIONED     VARCHAR2 (3 Byte)
IOT_TYPE     VARCHAR2 (12 Byte)
TEMPORARY     VARCHAR2 (1 Byte)
SECONDARY     VARCHAR2 (1 Byte)
NESTED     VARCHAR2 (3 Byte)
BUFFER_POOL     VARCHAR2 (7 Byte)
ROW_MOVEMENT     VARCHAR2 (8 Byte)
GLOBAL_STATS     VARCHAR2 (3 Byte)
USER_STATS     VARCHAR2 (3 Byte)
DURATION     VARCHAR2 (15 Byte)
SKIP_CORRUPT     VARCHAR2 (8 Byte)
MONITORING     VARCHAR2 (3 Byte)
CLUSTER_OWNER     VARCHAR2 (30 Byte)
DEPENDENCIES     VARCHAR2 (8 Byte)
COMPRESSION     VARCHAR2 (8 Byte)
DROPPED     VARCHAR2 (3 Byte)

Finding common attributes in a table

Finding common attributes in a table
Hello,
I am sometimes faced with the following problems and I don’t know if it can be solved with SQL or how it could be solved with PL/SQL. I appreciate your help on this.
I have a customer table with a cust_id key and 10 their customer attributes in the table.
1.     Given a set of cust_id keys, what are the common attributes of that set. That is, of the other 10 attributes, which ones are the same for each cust_id in the set?
2.     Given a set of attributes, what is the set of cust_id keys for which they are all the same?
Thanks for your help and suggestions.
Gary

Something like:
select case
          when min(attr1) = max(attr1) then 'All attr1 values are ' || max(attr1)
          else 'Attr1 values range form ' || min(attr1) || ' to ' || max(attr1)
        end attr1,
        case
          when min(attr2) = max(attr2) then 'All attr2 values are ' || max(attr2)
          else 'Attr2 values range form ' || min(attr1) || ' to ' || max(attr2)
        end attr2,
        case
          when min(attr10) = max(attr1) then 'All attr10 values are ' || max(attr10)
          else 'Attr10 values range form ' || min(attr10) || ' to ' || max(attr10)
        end attr10
from customer
where cust_id in (cust_id_set)
select cust_id
from customer
where attr1 = attr1_val
/SY.
P.S. You need to tell how you wnat to treat NULL values.

Date field is missing in the Table maintainance generator

Hi,
A table is created. A date field is there in that table. I tried to create a table maintainance generator for this table using 2 screens. Table maintainance generator is created. But when I go to SM30 , I am unable to see this DATE field in the SM30 , in the first screen. But when I go to maintainance screen , I am able to see this field. This particularly happening with date field.
Could you please help me.
Regards,
Satya

go to se11 and type the table what you want.
utilities, table maintenance generator.
you config the options that you need.
press F6 and go to sm30.
its only this.
Regards

Change Documents for the table EKET

Hi ,
We create a purchase order from ME21N . We do have some data for delivery schedule for the data .
This delivery schedule data gets stored in tabe EKET . When this PO is processed from V_V2 the dates
in the delivery schedule are overwritten and he new values will be even in the table EKET . When I follow
the navigation Environment -> Item Changes I dont see the changes documents for these fate fields . I did
debug through the FM EINKBELEG_WRITE_DOCUMENT to see but it looks like it is not captuirng the fields .
Now my requirement is to find where the change documents can be found for the date changes in the delivery
schedule tab in the PO . The fields of interest are :
EKET-SFLDT , EKET-DAT01, EKET-MBDAT , EKET-LDDAT , EKET-WADAT .
I tried for some OSS notes too, but in vain . Can anyone please help to find out how we find the changes documents for these fields .
Also please tell me if there are any OSS notes which explain us to extend the table EKET .
Thanks and Regards ,
Varun .

HI ,
I did check the table CDHDR and CDPOS and also the change document is checked for the data element but no change documents are stored in CDHDR and CDPOS .
Did anyone ever extend the tabke EKET ? Any OSS notes available for this .
Regards ,
Varun .
Message was edited by: varun sonu

When it is beter to buffer the table

hi
when it is beter to buffer the table

Hi
Table buffering
Advantages of buffering
Concept of buffering
Buffering types
Buffer synchronization
Database access using Buffer concept
Buffering allows you to access data quicker by letting you
access it from the application server instead of the database.
Advantages of buffering
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.
Concept of buffering
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.
Buffering types
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.
Synchronizing local buffers
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.
Using buffered tables improves the performance considerably.
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'.
Optimizing the load of the database
Using table buffering
 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.
Reward if useful

Attribute of the Master Table in the Selection screen

Hi Experts,
I'm maintaining a Material Master table with all these attributes
MATERIAL CODE -
Material Description
Material Group
Material Price
Material Type
In my transaction table only the material code is loaded along with the other transactions and the material group, price or description is viewed in report as I'm maintaining the master.
If I want to view only the Group G1in the report. Can I bring this group in the selection screen to view only those details of the transation belong to the respective group?
Since I'm maintaining the group in master table. Will the selection variable consider the attribute of the Transaction Field (Material)?
I'm not very sure whether it is possible.
Can anyone please adive me.
Thanks

HI,
IF you want to view the report based Material Group with out the MATERIAL CODE
then you want to make the Material group as navigational attribute.
Regards,
Sankar Reddy

Regarding buffering in techanical attributes of the table

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