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Posted by Ed Murphy on 01/14/08 05:34
Erland Sommarskog wrote:
> Ed Murphy (emurphy42@socal.rr.com) writes:
>> A couple users at one client are complaining of early morning
>> slowness in their OLTP system. The first thing that came to
>> mind is that the nightly backup might be using close to 100% of
>> the memory cache. (IIRC, they have 16 GB of RAM, 12 of which
>> is reserved for MSSQL, while the DB is roughly 30 GB.)
>>
>> Is there a way to limit how much memory cache the backup uses? (It
>> only takes about 15 minutes now, so we can afford to slow it down
>> in order to speed user operations up.)
>
> I would first analyse whether the problem is really due to that cache having
> been flushed.
How would I go about that? Profiler trace, looking for lots of cache
misses during the early morning?
> If that really is the case, I would investigate what might be flushing the
> cache. I don't know for sure, but I don't think it's the backup. They could
> have some nightly batch jobs that slurps memory. Or for that matter, they
> may be defragmenting tables every night. (And who knows: may be the
> reindexing has started to spill into early morning, and that's why the
> users find the system slow.)
There are some nightly batch jobs, though nothing comes to mind that
would obviously have this level of impact. I'll have to poke at it
some more this coming week.
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