>Just a general question.........With Disk caching enabled , does this slow
>down a backup operation. I know it requires
>more DB space but can't see any documentation that says it will impede a
>backup operation.

The performance implications are described in the Admin Guide section
"The Use of Cache on Disk Storage Pools".  The name "cache" in conjunction
with disk storage pools is somewhat misleading, in that the storage pool is
not treated as a write-through cache: file copies are instead retained when
migration has to occur.  *SM storage pool caching is more typically used on
Archive storage pools, where it is more customary to retrieve files.  Doing
caching on Backup storage pools may not be warranted unless you really need
it and are configured such that a day's backups fit within the storage pool
space.  Otherwise you need to employ the regiment of keeping your migration
thresholds low to retain enough storage pool space to keep up with the
incoming data.  And if you do have caching turned on and *SM has to make
space by disposing of a cached file, it has to take a little time to dismiss
the entry from the database and update the storage pool control blocks in
server memory.  It all comes down to how much you want to pay to achieve a
certain configuration objective.
   Richard Sims, BU