Is there a recommended value for SYSLOCKS in the SYSTEM statement of the SYSGEN and is there any negative impact of increasing it?
Locking overflow indicated by DC015007 messages on pool 255.
As of PTF RO97690 (r19.0 only) you may also get a number of DC040107 messages to warn that Lock Overflow allocations are being written to POOL 255.
(Note: RO97690 has a bug in it which is fixed by SO04177).
DC040107 LOCK MANAGER SECONDARY STORAGE REQUESTED
The recommended value for SYSLOCKS is 100,000 at the very least.
Some sites have been known to have it set as high as 1,000,000 or even more.
SYSLOCKS is not a number of locks of a certain size. It is a numerical seed used in a calculation which also involves other aspects of the sysgen which might indicate the size of the CV (e.g. MAXTASKS, number of LTERMs etc). These values are used to calculate an amount of storage allocated at startup to be used for locking.
This storage is above the line, operating system storage – i.e., it is not taken from the CV’s storage pools defined in the CV.
If this storage is exhausted, then overflow locking storage is taken from pool 255 – the CV’s system XA storage pool.
The amount of storage allocated at startup can be seen in the DC040102 message on the CV joblog:-
IDMS DC040102 V65 LOCK MANAGER STORAGE FORMATTED; 4476K USED
The only downside of increasing SYSLOCKS is that this amount of storage will be larger and so the CV will use more 31-bit operating system storage. To check how much the CV is using, see How to know how much 31bit storage used by IDMS CV.