ADSM-L

CHECKIN LIBV in 3494 robot - optimising

1997-04-25 12:48:32
Subject: CHECKIN LIBV in 3494 robot - optimising
From: "BELL, CRAIG" <rcbell AT VNET.IBM DOT COM>
Date: Fri, 25 Apr 1997 09:48:32 PDT
This is an oft-complained about problem that one day WILL be fixed!  The
CHECKIN, CHECKOUT, and AUDIT commands are library-mgmt only functions
that do not acquire drives the same way normal storagepool volumes use
them.  Checkins  "steal" a drive away to do the checkin, and they do
this in a way that the storagepool mounts can wait for them (so that
backup/restores are not preempted for a checkin).  The down sides of the
current implementation are (1) only one drive is used at a time for
checkins (no matter how many you run) (2) checking in a single volume
grabs a drive right away and any pending storagepool mounts have to wait
for it to finish (3) issuing several checkins means they ALL have to
complete before any storagepool mounts can be serviced, and (4) if all
the drives are mounted IDLE with storage pool volumes, CHECKIN will not
dismount them the way storagepool mounts will.  You have to issue the
DISMOUNT VOLUME command yourself.

However, these problems will not be encountered if you use CHECKIN with
SEARCH=YES and CHECKLABEL=NO, so I would recommend it if you can.  Or
use this information to better schedule your single volume checkins
(only do it one at a time, and when you think there won't be heavy
storage pool activity).  I think that checking the label is really not
neccessary unless you think a volume has never been labelled, or you
want to double check.  The label is always checked on storagepool mounts
anyway, and we never erase them once labelled.

For AUDIT LIBRARY, audits have to wait for all current jobs are done and
dismounted before it will run, and no mounts can take place until it's
finished.

Craig Bell