As administrator, you therefore have no power over when a lock entry is created or deleted. Nevertheless, it’s extremely important that you understand the SAP lock mechanism because you may have to delete orphaned lock entries. The lock mechanism works closely with the update mechanism.
There are different types of locks:
Write locks (E): This is also known as exclusive lock mode as the lock data can be edited by only one user. Any other requests from work processes to set another write lock or read lock are rejected. A cumulate lock can be applied on the lock data by the same lock owner again.
Read locks (S): This is also known as shared lock mode as several users can have read access to the locked data at the same time. Additional read lock requests are entertained even if they are from different users. However, a write lock is rejected.
Enhanced write locks (X): This is also known as exclusive non-cumulative lock mode. An enhanced write lock can be requested only once even if it is by the same transaction.
Difference between write locks (E) and Enhanced write lock (X) is: write locks can be set and released by the same transaction several times but X type locks can also be set once even by the same transaction.
Optimistic locks (O): These locks are set up when the users display the data in change mode. Several optimistic locks can be setup on the same data. Optimistic locks are read locks (S), and later converted to write lock (E) when the user wants to save the data. If an optimistic lock on a data is changed to write lock (E), all other optimistic locks on that data will be deleted.
Locks that are set by an application program are released by the program itself or they are released by the update program once the database has been changed.
Transaction code SM12 can be used to monitor SAP locks.
:analysis
sm13 is for update wp monitoring.
in which we can retry the updates.
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