[Info-vax] DIRCACHE hit rate.

[Jan-Erik Söderholm]

Hein RMS van den Heuvel wrote:
> On Jan 20, 12:08 pm, 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
> 
> That seems supspiciously low.
> This statistics is across all drives.
> Are there MD (DECram) disks in play?
> Are there any disks mounted /nocache ?

No and no (as far as I know). There are a couple
of LD disks mounted but not used at the moment.
(Python distribution)

> 
> If there is such a thing a 'typical' batch job in your environment
> then I would
> want to run one with SET WATCH FILE/CLA=MAJOR or /CLA=ALL to 'see'
> whether any surprises access are attempted.

All batch jobs a more or less pure DCL with a few tools
such as ZIP/UNZIP and MPACK/MUNPACK used to process mails
with attached files.

> 
> I also find the SDA extention 'LNM' very 'handy' in tracing file
> (attempted) file access.
> 
>> Another thing is that all files are timestamped in the filename, so there are normaly only ;1 files.
> 
> Not sure how that is good or bad.
> Multi-version fiels are MORE efficient that many single-version files,
> from a directory space perspective. Can't get any thighter then an
> entry in an 8 byte entry to store a fresh version + file-id.
> 
> Is the application using a 'nice' timestamp like a leading
> yyyymmddhhmm allowing for adding/activity to the end only, or leadin-
> names or dd-mmm-yyyy stamps leading to random inserts?

They have a leading name with yyymmmdd.... appended someplace in the
middle or at the end and typicaly all are called ".tmp" (if it matters).

> 
> Are temporary files alphabetically mixed with main files in the same
> directory?

It's a temp-directory only. Other dirs has the code and config files.

> Ever tried a dedicated (pre-allocated) directory for the temporary
> files?
> There are multiple disks... are they all being used by all batch jobs
> or is it the typicaly silly setup with a directory(s) on a single disk
> for each user/application/batch-job?
> 
> What tools is creating the (temp) files? DCL $OPEN/WRITE,

Mostly DCL OPEN. No C. Some by other utilites like ZIP, UNZIP,
MPACK, MIME, MUNPACK and so on.

> C create?
> The C-RTL adds a lookup to see whether a file with that name exists to
> allow attribute inheritance. (nasty feature imho).
> 
>> 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.
> 
> I doubt it, but would certainly encourage going to 8.3 (skip 8.2!).
> Lot's of nice stuff there.

Yes, I know. :-)  We'll probably do that anyway...

Thanks !

Jan-Erik.
> 
> Hein.