stgpool migration starts 2nd scratch tape?

Hmm.  Why would ADSM start a 2nd tape (during a normal stgpool
migration) when the (first) tape it's been writing to is still
present and enabled?  In the following log, we first write to D0012 a
couple of times, then dismount it, and then _remount_ it (in the other
drive), but also mount a new scratch volume (D0013) and decide to write to
that.

Is there some parameter I should be setting?  I'd expected everything to
write on one tape (only 17GB of data, and we've got 35GB DLT tapes).  D0012
is now 41% full, still R/W access, and in the "filling" state.

Thanks.

Pat Wilson
paw AT dartmouth DOT edu

I see:

        10/05/1998 12:39:31  ANR0984I Process 723 for MIGRATION started in the
                              BACKGROUND at 12:39:31.
        10/05/1998 12:39:31  ANR1000I Migration process 723 started for storage 
pool
                              AFS_B_POOL.
        10/05/1998 12:40:44  ANR8337I DLT volume D0012 mounted in drive DRIVE01 
(/dev/mt0).
        10/05/1998 12:40:44  ANR1340I Scratch volume D0012 is now defined in 
storage
                              pool AFS_B_TAPEPOOL.
        10/05/1998 12:55:15  ANR1001I Migration process 723 ended for storage 
pool
                              AFS_B_POOL.
        10/05/1998 12:55:15  ANR0986I Process 723 for MIGRATION running in the
                              BACKGROUND processed 2361 items for a total of
                              1,950,375,936 bytes with a completion state of 
SUCCESS at
                              12:55:15.
        10/05/1998 13:44:44  ANR0984I Process 724 for MIGRATION started in the
                              BACKGROUND at 13:44:44.
        10/05/1998 13:44:44  ANR1000I Migration process 724 started for storage 
pool
                              AFS_B_POOL.
        10/05/1998 13:54:58  ANR1001I Migration process 724 ended for storage 
pool
                              AFS_B_POOL.
        10/05/1998 13:54:58  ANR0986I Process 724 for MIGRATION running in the
                              BACKGROUND processed 177 items for a total of
                              2,031,878,144 bytes with a completion state of 
SUCCESS at
                              13:54:58.
        10/05/1998 14:12:19  ANR8329I DLT volume D0012 is mounted R/W in drive 
DRIVE01
                              (/dev/mt0), status: IDLE.
        10/05/1998 14:12:19  ANR8334I   1 volumes found.
        10/05/1998 15:22:06  ANR0984I Process 725 for MIGRATION started in the
                             BACKGROUND at 15:22:06.
        10/05/1998 15:22:06  ANR1000I Migration process 725 started for storage 
pool
                              AFS_B_POOL.
        10/05/1998 15:30:43  ANR1001I Migration process 725 ended for storage 
pool
                              AFS_B_POOL.
        10/05/1998 15:30:43  ANR0986I Process 725 for MIGRATION running in the
                              BACKGROUND processed 1410 items for a total of
                              1,851,084,800 bytes with a completion state of 
SUCCESS at
                              15:30:43.
        10/05/1998 16:30:47  ANR8325I Dismounting volume D0012 - 60 minute mount
                              retention expired.
        10/05/1998 16:31:09  ANR8336I Verifying label of DLT volume D0012 in 
drive
                              DRIVE01 (/dev/mt0).
        10/05/1998 16:33:09  ANR8468I DLT volume D0012 dismounted from drive 
DRIVE01
                              (/dev/mt0) in library AUTODLTLIB.
        10/05/1998 16:38:43  ANR0984I Process 726 for MIGRATION started in the
                              BACKGROUND at 16:38:43.
        10/05/1998 16:38:43  ANR1000I Migration process 726 started for storage 
pool
                              AFS_B_POOL.
        10/05/1998 16:39:56  ANR8337I DLT volume D0012 mounted in drive DRIVE02
                              (/dev/mt1).
        10/05/1998 16:41:05  ANR8337I DLT volume D0013 mounted in drive DRIVE01
                              (/dev/mt0).
        10/05/1998 16:41:06  ANR1340I Scratch volume D0013 is now defined in 
storage
                              pool AFS_B_TAPEPOOL.
        10/05/1998 16:50:11  ANR1001I Migration process 726 ended for storage 
pool
                              AFS_B_POOL.
        10/05/1998 16:50:11  ANR0986I Process 726 for MIGRATION running in the
                              BACKGROUND processed 344 items for a total of
                              1,927,700,480 bytes with a completion state of 
SUCCESS at
                              16:50:11.