Subject:ADSM TAPE CAPACITY

>>I have a question for you. I am currently using  ADSM MVS-SERVER VER.
>>3.1.1.3 to backup on SILOS STK. I had define into device class device=3490
>>and maxcapacity=650Mb. In this situation the command Q VOLUME seem me
>>maxcapacity=500Mb full. I don t undusted why.
>>Can You help me?

On VM and MVS servers MAXCAPACITY is the maximum amount of data that ADSM will
put on a tape, but if the tape becomes physically full, or has certain errors,
it will be marked full before it reaches that capacity.  The capacity reported
by ADSM does not consider compression.  If client compression is used, or if
the data is not very compressible (backups of zip files, for examples)
then ADSM will report a full tape will a smaller capacity.  Most tape
manufacturers give their tape capacity assuming compression (I think normally
around 3/1), so if you are sending already compressed data, you will not be
able to reach the stated capacities.

MAXCAPACITY, if set to other than 0 determines the maximum amount of data
ADSM will put to a tape, ESTCAPACITY, if MAXCAPACITY is not set, is an estimate
used for some calculations for reclamation and display, but does not determine
when a tape is full. For further information on the MAXCAPACITY and ESTCAPACITY
parameters of the DEFINE and UPDATE DEVCLASS command, see the Administrator's
Reference, or use the online help.

Carol Trible
ADSM Development