How to create Lock objects?
What is the main use of it in real time?
Lock objects are use in SAP to avoid the inconsistency 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 through 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 maintenance screen SAP can't allow to any other user to use same personal number for changes.
Technically:
When you create a lock object System automatically create
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.
You have to use these function module in your program.
Structure of a Lock Object
The tables in which data records should be locked with a lock request are defined in a lock object together with their key fields. When tables are selected, one table (the primary table) is first selected. Further tables (secondary tables) can also be added using foreign key relationships.
For example:
The user goes to VA02 to change a sales order, in this program, a lock is set. You can see such locks in transaction SM12. If a lock is set, and another user accesses the same sales order, then they will get a message saying that the sales order is locked. The ENQUEUE function module is used to set the lock, the DEQUEUE function module is to release the lock.
