[Info-vax] DIRCACHE hit rate.

[Richard B. Gilbert]

Jan-Erik Söderholm wrote:
> IanMiller wrote:
>> On 20 Jan, 17:08, Jan-Erik Söderholm <jan-erik.soderh... at telia.com>
>> wrote:
>>> Hi.
>>> I have an 7.3-2 Alpha system where I think that
>>> the hit rate on the DIR-cache is way to low.
>>>
>>> DS20 with 9GB disks in BA356 shelfs.
>>>
>>> Here is what it typicaly looks like :
>>>
>>>                         CUR     AVE   MIN      MAX
>>>   Dir Data (Hit %)     3.00    3.20  0.00    30.00
>>>       (Attempt Rate) 312.00  548.90  0.00  2460.00
>>>
>>> The ACP_DIRCACHE is at the moment at 4000 (blocks)
>>> but I have raised it to 10000 without any measurable
>>> improvment.
>>>
>>> Yes, there are a few DIR's that are "large", but not
>>> *that* large, maybe 5-10.000 files and a few DIR files
>>> of 1-2000 blocks. Another thing is that all files
>>> are timestamped in the filename, so there are
>>> normaly only ;1 files.
>>>
>>> My batch jobs create a number of temp files during
>>> processing and I've got a feeling that this is
>>> slowing them down a bit.
>>>
>>> Now, what I'd like to ask, is if anyone knows if
>>> this part of VMS has had any major improvments in
>>> the 8.x versions ? We are currently thinking of
>>> upgrading anyway, and it would be nice to know
>>> if these hit rates would improve simply by upgrading.
>>>
>>> Best Regards,
>>> Jan-Erik.
>>
>>
>>
>> What's the real issue? Is the time taken for your batch jobs too long?
> 
> Well, It's manageable right now, but I think that the jobs runs
> aprox 2 times long as needed. I see some run-time reduction when
> I create a new temp-directory and re-define the temp-logical to
> that empty directory, but after a while it's back where
> it begun, of course.
> 
>  From some other replies in this thread I've come to this conslusion:
> 
> If I want a timestamp in the filename, it's better to have it in the
> beginning, so all new file creations will happend at the end of
> the DIR file. Say I have 5 temp files called A, B, C, D and E.
> I have a timestamp "ts" like "yyyymmddhhmmsshh". Then files called
> 
> dev:[dir]'ts'_A.TMP
> dev:[dir]'ts'_B.TMP
> dev:[dir]'ts'_C.TMP
> dev:[dir]'ts'_D.TMP
> dev:[dir]'ts'_E.TMP
> 
> are better then
> 
> dev:[dir]A_'ts'.TMP
> dev:[dir]B_'ts'.TMP
> dev:[dir]C_'ts'.TMP
> dev:[dir]D_'ts'.TMP
> dev:[dir]E_'ts'.TMP
> 
> Lets also say that there are 1-2000 A-files, B-files
> ans so on.
> 
> Right ?
> 
> Another way would be to have temp directories called [dir.yyymmdd]
> so that there is a new directory for each day, or something lie that.
> 

A directory per day or per week or even per month, sounds like a 
workable solution to me.  How long do you have to keep this stuff on 
line?  How often do you need to access it?