Re: Sporadic Performance Issue v7r5

Hello Greg,

Am 07.12.2023 um 18:13 schrieb Greg Wilburn <gwilburn@xxxxxxxxxxxxxxxxxxxxxxx>:

When this degredation occurs, WRKSYSACT sorted by I/O shows SMPOL001 at the top with 20K Non-DB Write over about 15 minutes.

Found this when searching for SMPOL001:

https://archive.midrange.com/midrange-l/200110/msg00105.html

The coincidence of your observed behavior happening after the upgrade is a mystery, because the applications should behave as before.

If we can't nail this down, our alternative is a relatively pricey upgrade that involves a new box and jumping up a processor group.

I'm not yet sure if this would help.

It might be interesting to find out what triggers this sudden massive writeback. Apparently, a lot of changed data has accumulated in RAM. Why this isn't written back steadily in the background I don't know. I think, this has happened with the earlier release (possibly needing less RAM for itself) and so you didn't notice.

Maybe Richard Theis' hint is towards the right direction? Accumulated dirty pages reach a certain threshold count and are then written back with higher priority, in turn affecting everything else. More RAM *could* help. Or closely review your pool definitions. Or both. :-)

Just thinking out loud here…

:wq! PoC