David,

for what it is worth,

Here is a excerpt from a 'q vol' of some tapes marked as full from my
system.
----------------------------------------------------------------------------
-----
-----
Volume Name               Storage      Device      Estimated    Pct   Volume
Volume Name               Storage      Device      Estimated    Pct   Volume
                          Pool Name    Class Name   Capacity   Util   Status
                                                        (MB)
------------------------  -----------  ----------  ---------  -----
--------
--------
C00083                    TAPEPOOL     TAPE3590    203,025.7  100.0    Full
C00083                    TAPEPOOL     TAPE3590    203,025.7  100.0    Full
C00084                    TAPEPOOL     TAPE3590    152,142.7   42.2    Full
C00086                    OFFSITE      TAPE3590    195,116.3   95.4    Full
C00087                    TAPEPOOL     TAPE3590    206,932.1   65.6    Full
C00093                    TAPEPOOL     TAPE3590    196,629.9   34.1    Full
----------------------------------------------------------------------------
-----
-----
Most of the backups are of Oracle DB on an AIX platform.  If I take into
Most of the backups are of Oracle DB on an AIX platform.  If I take into
account the size of the data being backed up and the est. cap. of the tapes,
once full, I would have to say that the est. cap. is fairly accurate.

Jim Taylor