[Info-vax] DIRCACHE hit rate.

[Jan-Erik Söderholm]

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.

Jan-Erik.