topic Re: MON CLUS query in Operating System - OpenVMS

MON CLUS query

Paul Taylor_6 — Thu, 06 Apr 2006 05:22:59 GMT

Running a 3 node cluster under VMS7.2.
2 primary nodes have exactly same sysgen settings and values. Each of 2 nodes have disk arrays mirrored to the 'paired' node.
Nodes seem reasonably well balanced, but when issuing MON CLUS command, the results reported in the 'LOCK' quadrant are severely imbalanced; 1 node reporting tot ENQ/DEQ rates that are at times 10x higher than its partner node. Could anyone please shed light on how these stats should be interpreted?

What value(s) can be considered good/bad?
What sysgen parameter - if any - affects this?
Is it expected to have such relative differences in a cluster that we're attempting to balance.

Would appreciate any advice at all please.

Re: MON CLUS query

Volker Halle — Thu, 06 Apr 2006 05:41:12 GMT

Paul,

lock ENQs (and DEQs) are done by 'the applications'. If the applications are making sensibly use of locking, higher rates would indicate higher application load, which would be 'good'.

You could use MONI LOCK and MONI DLOCK to try to find out, what kind of lock operations are happening and whether there is a lot of 'remote' locking instead of local locking.

There could also be lock re-mastering, but the MONI RLOCK command is not available in V7.2, should would have to look at the RM counters with SDA> SHOW SYMB/ALL PMS$GL_RM

Local locking will just consume kernel mode CPU time, remote locking will also add interrupt mode time and use cluster interconnect bandwidth.

Volker.

Re: MON CLUS query

Phil.Howell — Thu, 06 Apr 2006 20:45:04 GMT

If your system has files that are opened on more than one node, then the first node that opens a file becomes the "lock mastering node" for that file, and has to handle both local lock processing and locks taken out by the "other" node.
If your system has mostly "local" file processing then the lock rates are probably just an indication of RMS file activity.
Setting up RMS statistics and monitoring on "hot" files can be used to check this.
The RMS_DEFAULT settings can have an effect on the number of locks, more buffers=more concurrent locks.
I wouldn't worry about enq/deq rates until they are > many thousand per second.
Phil

Re: MON CLUS query

labadie_1 — Fri, 07 Apr 2006 05:34:59 GMT

As you are before Vms 7.3, you should use the program available at
http://h18000.www1.hp.com/support/asktima/operating_systems/009F6DF1-BC7EC4E1-1C02A1.html

[OpenVMS] Example-C How to Monitor

the Dynamic Lock Remastering Activity

This is the monitor rlock for before Vms 7.3 (which has seen monitor rlock appear)