In SAP data is locked by the system while it is being edited by a user. Which prevents other users changing the record at the same time. In some cases the lock entries will exist in the system due to system failure.
The lock entries can be removed manually from the system by following transaction code SM12
1) Enter the transaction code SM12 in command field and press enter
2) Enter the relevant parameter provided and click the list button
3) Analyze the lock entries and if any previous date entries exist in the system. It has to be cleared by manually deleting
4) Double click on the lock entry and list the detail view for further details.
5) To delete the lock entries select the entry and press delete button as shown below.
In the dialog box choose yes to confirm and the lock entry will be released with the following message.