Hi all,
The 'old' redbook "Getting started with ADSM: A practical Implemantation
Guide" recommends to use a seperate MC and STP for directories (for restore
performance reasons). Chapter 13.2.3 DIRMC (page 236) states:
"In a restore ..., ADSM first restores the directories and then the
files..."
(This chapter is identical in the newer "Getting started with TSM:
Implementation Guide.)
However there are DIRMC disadvantages as well; recently a known DIRMC
performance problem was described by NORBERT WINDRICH:
>we made a move data of a dirmc copy pool. The move data process
>needs 5:12 hours to move 70 823 172 bytes. Most of the data is read
>from a disk storage pool. For database files we can move up to 10 GB
>per hour.
At out site we have the same problem (caused by tape repositioning zillion
times) , but with migration. Fortunately BILL BOYER responded with the
following AND a solution:
>A co-worker of mine worked with IBM/Tivoli on this. The symptoms came
during
>the reclamation of the offsite copypool tapes for the DIRMC disk storage
>pool. The answer he got was that reading from the disk storage pool was
done
>a file at a time and not buffered. They said it was because it was a random
>access device and they had no plans to 'fix' it.[...]
>What he came up with was to create a sequential primary pool with a FILE
>device class and make this the NEXTSTGpool for the DIRMC disk pool and
>migrate daily. The reclamation and BA STG are alot faster.[...]
>The reclamation [...] runs in about an hour [...] instead of a day.
This solution sounds perfect and should work (not repeated yet), but ... is
there still a need for DIRMC after RICHARD SIMS kicks in?:
[...]
> Consider also that dirmc isn't what it once was. ADSMv3
>introduced the concept of Restore Order. See that entry in
>http://people.bu.edu/rbs/ADSM.QuickFacts, or APAR IC24321.
So, i looked up this entry in the QuickFact to find (try to find this in the
TSM manuals...):
[...]"restore order" considers where objects
exist on sequential media and brings
them back in this order so that the
media can be moved from beginning to
end. One of the side effects of this[...]
This suggest that (in V3) files and directories are retrieved just as the
come along on the media, contrary to the redbook suggestion ("In a restore
..., ADSM first restores the directories and then the files..."), however
the APAR text is not completely clear to me. If the redbook is correct, a
seperate pool for DIRMC makes sense. If the redbook in not correct, it
seems there is no justification for a DIRMC pool.
In the last case we would all be better off just leave the
complicated-but-not-so-usefull feature!
This leaves me with two Questions:
1) Is the use of DIRMC obsolete? (complex, but no advantage) (of course we
can always 'make up' some advantage, like 'its nice tho have the dirtree
seperate..')
2) If the redbook is incorrect, but if DIRMC is still used (with seperate
STG) how will a restore work, first the DIRMC STP, then the file STP or
what?
Allshare Personnel BV
Jochem van Hal
mailto:[EMAIL PROTECTED]
www.allshare.nl
tel +31 (0) 23 569 22 21
mob +31 (0) 6 21 588 423
fax +31 (0) 23 569 22 99
