Deepshika,
This warning message is stating that one of the STMM parameters could not be adjusted for some reason. STMM was either trying to increase one of the parameters but the memory was not available or STMM was trying to decrease one of the parameters but for some reason could not.
The STMM log should provide you with more information. It is located in /sqllib/db2dump/stmmlog. Look to see what parameter was trying to be adjusted during the timestamp in the db2diag.log.
Also make sure all of the STMM parameters are set to AUTOMATIC including all of the bufferpools.
If all else fails then open a PMR with IBM.
Thanks,
Eric Sheridan