Where we use lock objects in our coding like report

Question

what is the purpose of lock objects s? how we use them in real time? like in devoloping reports?

Answer 1

Hi,,.
Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.
SAP Provide three type of Lock objects.
- Read Lock(Shared Locked)
protects read access to an object. The read lock allows other transactions read access but not write access to
the locked area of the table
- Write Lock(exclusive lock)
protects write access to an object. The write lock allows other transactions neither read nor write access to
the locked area of the table.
- Enhanced write lock (exclusive lock without cumulating)
works like a write lock except that the enhanced write lock also protects from further accesses from the
same transaction.
You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.
Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.
Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.
Technicaly:
When you create a lock object System automatically creat two function module.
1. ENQUEUE_<Lockobject name>. to insert the object in a queue.
2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.
Check these links
Re: Lock Objects
http://help.sap.com/saphelp_47x200/helpdata/en/ce/931bb5c79911d5993e00508b6b8b11/frameset.htm
http://help.sap.com/saphelp_47x200/helpdata/en/e1/8e51341a06084de10000009b38f83b/frameset.htm
http://www.sapdevelopment.co.uk/dictionary/lock_enqueue.htm
http://help.sap.com/saphelp_nw04/helpdata/en/a2/3547360f2ea61fe10000009b38f839/frameset.htm
http://help.sap.com/saphelp_nw04s/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm
http://www.sap-img.com/abap/type-and-uses-of-lock-objects-in-sap.htm
http://help.sap.com/saphelp_nw04s/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm
Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.
SAP Provide three type of Lock objects.
- Read Lock(Shared Locked)
protects read access to an object. The read lock allows other transactions read access but not write access to
the locked area of the table
- Write Lock(exclusive lock)
protects write access to an object. The write lock allows other transactions neither read nor write access to
the locked area of the table.
- Enhanced write lock (exclusive lock without cumulating)
works like a write lock except that the enhanced write lock also protects from further accesses from the
same transaction.
You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.
Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.
Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.
Technicaly:
When you create a lock object System automatically creat two function module.
1. ENQUEUE_<Lockobject name>. to insert the object in a queue.
2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.
Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.
SAP Provide three type of Lock objects.
- Read Lock(Shared Locked)
protects read access to an object. The read lock allows other transactions read access but not write access to
the locked area of the table
- Write Lock(exclusive lock)
protects write access to an object. The write lock allows other transactions neither read nor write access to
the locked area of the table.
- Enhanced write lock (exclusive lock without cumulating)
works like a write lock except that the enhanced write lock also protects from further accesses from the
same transaction.
You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.
Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.
Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.
Technicaly:
When you create a lock object System automatically creat two function module.
1. ENQUEUE_<Lockobject name>. to insert the object in a queue.
2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.
http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm
GO TO SE11
Select the radio button "Lock object"..
Give the name starts with EZ or EY..
Example: EYTEST
Press Create button..
Give the short description..
Example: Lock object for table ZTABLE..
In the tables tab..Give the table name..
Example: ZTABLE
Save and generate..
Your lock object is now created..You can see the LOCK MODULES..
In the menu ..GOTO -> LOCK MODULES..There you can see the ENQUEUE and DEQUEUE function
Lock objects:
http://www.sap-img.com/abap/type-and-uses-of-lock-objects-in-sap.htm
http://help.sap.com/saphelp_nw04s/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm
Match Code Objects:
http://help.sap.com/saphelp_nw2004s/helpdata/en/41/f6b237fec48c67e10000009b38f8cf/content.htm
http://searchsap.techtarget.com/tip/0,289483,sid21_gci553386,00.html
See this link:
http://www.sap-img.com/abap/type-and-uses-of-lock-objects-in-sap.htm
Lock objects are used to synchronize access to the same data by more than one program.
General information about the lock mechanism.
You can synchronize access by several programs to the same data with a logical lock mechanism. This lock mechanism fulfills two main functions:
A program can tell other programs which data records it is just reading or changing.
A program can prevent itself from reading data that is just being changed by another program.
When accessing data records, the records just being edited by other programs can be identified by the entry in the lock table. Such an entry for the lock must define a number of fully specified key fields, that is either a value is passed for the key field or this field is locked generically.
To set locks, a lock object must be defined in the ABAP Dictionary. When this lock object is activated, two function modules (see Function Modules for Lock Requests) are generated with the names ENQUEUE_<lockobjectname> and DEQUEUE_<lockobjectname>.
If data records are to be locked, you must call function module ENQUEUE_<lockobjectname>. The values of the key fields that specify the records to be locked are passed for all the tables contained in the lock object when the function module is called. There is a generic lock if a value is not passed for all the key fields. The function module writes the appropriate lock entry (see Example for Lock Objects). If another program also requests a lock, it will be accepted or rejected depending on the lock mode (see Lock Collisions). The program can then react to this situation.
Locked data records can be unlocked by calling function module DEQUEUE_<lockobjectname>. The key values and the lock mode used to set the lock must be passed to the function module.
Creating Lock Objects
Procedure
Select object type Lock object in the initial screen of the ABAP Dictionary, enter an object name and choose Create. The name of a lock object should begin with an E (Enqueue).
The maintenance screen for lock objects is displayed.
Enter an explanatory short text in the field Short text.
You can then use the short text to find the lock object at a later time, for example with the R/3 Repository Information System.
Enter the name of the primary table of the lock object.
All other tables in the lock object must be linked with the primary table using foreign keys. There are also some restrictions on the valid foreign key relationships.
Select the lock mode of the primary table in the field below it.
The lock mode is used as the default value for the corresponding parameters of the function modules generated from the lock object.
Choose Add if you want to lock records in more than one table with the lock object.
A list of all the tables linked with the primary table using valid foreign keys is displayed. Select the appropriate table. The lock mode of the primary table is copied as lock mode. You can change this setting as required, for example you can assign the lock mode separately for each table.
Similarly, you can add a table linked with the secondary table just added with foreign keys. To do this, place the cursor on the name of the secondary table and choose Add.
If no lock mode is assigned to a table, no lock is set for the entries in this table when the generated function modules are called. You should not assign a lock mode if a secondary table was only used to define a path between the primary table and another secondary table with foreign keys.
Save your entries.
A dialog box appears in which you have to assign the lock object a development class.
You can (optionally) exclude lock parameters (see lock objects) from the function module generation on the Lock parameter tab page. This makes sense for example if you always want to lock a parameter generically.
To do this, simply deselect the Weight flag for the parameter. The parameter is not taken into consideration in the generated function modules. This parameter is then always locked generically.
The name of a lock parameter is usually the name of the corresponding table field. If two fields with the same name are used as lock parameters in the lock object from different tables, you must choose a new name for one of the fields in field Lock parameter.
You can define whether the function modules generated from the lock object should be RFC-enabled on the Attributes tab page.
If you set the Allow RFC flag, the generated function modules can be called from within another system with Remote Function Call.
If you permit Remote Function Calls for an existing lock object, you must ensure that the generated function modules are called from within an ABAP program with parameters appropriate for the type. You should therefore check all programs that use the associated function modules before activating the lock object with the new option.
Choose .
Result
When you activate the lock object, the two function modules ENQUEUE_<lockobjectname> and DEQUEUE_<lockobjectname> are generated from its definition to set and release locks.
Regards
Vasu