Re: Mixing SSD & Spinny

Hello Rob,

Am 02.07.2020 um 17:59 schrieb Rob Berendt <rob@xxxxxxxxx>:

A lots gets cached out. Even if you have a crud load of memory.

Why bother when the cached-out components were rarely used? Like, the pwrdwnsys *CMD really does not need to be in RAM all the time, to point to an extreme case.

Btw., in SLS, there's no "cached out". "Cached out" is the default. For that reason, after a while of usage, there's no "free space" in RAM, because all will be used for caching, eventually. See below.

Let's look at DSPSYSSTS.

Here you see a bunch of memory, about 134GB. Very low paging and faulting.

Yes, looks pretty good.

However let's look at this other part of DSPSYSSTS.
Current temporary used : 191816 M
Peak temporary used . : 207133 M
Roughly 200G of temporary storage. The amount your system will use for temporary storage is related to the amount of free space your system has. Our temp storage usage may be more than some other people's system size. And our peak was recently reset by an IPL.

I really wonder what "temporary storage" really means. I'd love to know your opinion about the relation of temp storage vs. free space. As far as I understand, because of SLS, there's no such thing as "% pagefile used" as in Windows (or % swap partitions used in Linux).

The only true indication of "add more RAM" is the amount of page faults happening. The threshold about when to take action might be highly dependent on the sysadmin panicking level upon seeing statistical data, and users complaining about slow response times. :-)

(On my 150, I'm almost always constrained by the CPU, and rarely by I/O. Eventhough i has "only" 192 MB of RAM.)

:wq! PoC

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