IRLM startup procedure options
You can control how Db2 uses locks by specifying certain options when you start the internal resource lock manager (IRLM).
About this task
When you issue the z/OS® START irlmproc command
, the values of the options are passed to the startup procedure for
the Db2 IRLM.
(If an option is not explicitly specified on the command, the value
of its corresponding installation parameter is used.)
The options that are relevant to Db2 locking are:
- SCOPE
- Whether IRLM is used for data sharing (GLOBAL) or not (LOCAL). Use LOCAL unless you are using data sharing. If you use data sharing, specify GLOBAL.
- DEADLOK
- The two values of this option specify:
- The number of seconds between two successive scans for a local deadlock
- The number of local scans that occur before a scan for global deadlock starts
- PC
- Ignored by IRLM. However, PC is positional and must be maintained in the IRLM for compatibility.
- MAXCSA
- Ignored by IRLM. However, MAXCSA is positional and must be maintained in the IRLM for compatibility.
The maximum amount of storage available for IRLM
locks is limited to 90% of the total space given to the IRLM private
address space during the startup procedure. The other 10% is reserved
for IRLM system services, z/OS system
services, and must complete
processes to prevent the IRLM address
space from abending, which would bring down your Db2 system.
When the storage limit is reached, lock requests are rejected with
an out-of-storage reason code.
You can use the F irlmproc,STATUS,STOR
command to monitor the amount of storage that is available for locks
and the MODIFY irlmproc,SET command to dynamically change the maximum
amount of IRLM private storage to use for locks. 