How to delete SAP lock entry in SM12

What is SAP lock entry.
 SAP Lock is set by the executing work process when user/jobs want to change the data in SAP.
Whenever a lock to be set the respective work process checks in the lock table. Whether a respective lock conflicts the existing entries in the lock table.

Types of Lock
Write Lock (E) : This is also known as exclusive lock mode as the lock data can be edited by only one user at a time.Any other request from work process to set another Write lock or Read lock are rejected.A cumulate lock can be applied on the lock data by the same owner again.

Read lock (S) :  This is also known as shared lock mode as several user can have read access to the locked data at the same time. Additional read lock requests  are entertained even if  they are from different user.However a write lock is  rejected.  

Enhanced lock (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.

Optimistic lock(O) :  These lock are set up when the users displays the data in change mode. Several optimistic locks can be set up on the same data.Optimistic locks are Read locks at first and converted to Write locks  when user want to save the data.if an optimistic lock  on a data changed to Write locks ,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 released by update program once the database has been changed

Transaction Code SM12 can be used to Monitor the SAP Locks.

Have you selecting the options below.

• Table name
• Lock Argument
• Client
• User name

If you encounter some old locks and after through analysis ,we would like to delete these.

Follow this ways.

1. Select the lock and delete form SM12 .
2. Identify the user who has set the respective lock and end the user session using SM04 Tcode.