SAP OSS note 1234847 mentions changing the WebDynpro parameter sap.locking.maxWaitInterval
What are the implications of setting this to 30 minutes or 1 hour?
Answer copied from https://forums.sdn.sap.com/message.jspa?messageID=8713259
As the note 1234847 explains, as soon as a request for a user session is processed, the user session is blocked for the duration of the request i.e. there is always at most one thread that has acquired the lock of a user session.
Concurrent requests which refer to the same user session (i.e. triggered from the same browser process) are serialized and processed one after each other. If there is a request which blocks or hangs due to some waiting/blocking condition, then other concurrently incoming requests are waiting for a certain period of time that the user session lock is released. If they can't acquire the user session lock after this time interval, the waiting thread terminates with a LockException error page.
In such cases, the "sap.locking.maxWaitInterval" is helpful. Depending on the requests, administrators can increase it.
In previous cases, we have had customers increase it from 100s to 300s (or 500s) in the Web Dynpro default.properties, depending on their need.This will not make the server processing time slow, but there will be anextra buffer time so that the user request can pass through.
Customers vary the values of the parameter depending on the long runningapplications.
More information is available: http://help.sap.com/saphelp_nwce71/helpdata/en/43/8a1a8ece230c8ce10000000a11466f/content.htm
SAP note 1113811 also provides some info..
However, if even after increasing this parameter, if there are locking issues, then this can be due to a application error. We will need to anayse a thread dump to check the status of the threads during the locking process. As you are aware, it is the java threads that are responsible for the actual carrying out of the server tasks, akin to the ABAP work processes.
SAP Note No. 710154-How to create a thread dump for the J2EE Engine