Patrice
   Just be sure and do a test restore to make sure Veritas restores the file
identically to the original :-0
   There have been problems where systems see "unused" space in Oracle data
files and eliminate it to save you some space. Oracle doesn't see the humor
;-)

Dennis Williams
DBA, 40%OCP, 100% DBA
Lifetouch, Inc.
[EMAIL PROTECTED] 


-----Original Message-----
Sent: Wednesday, March 19, 2003 8:09 AM
To: Multiple recipients of list ORACLE-L


[/begin rant]
We ran into a bit of a puzzle here.

It started innocently enough, with someone asking whether Oracle tablespaces
that are largely empty are really being compressed before they are written
to tape.

We use Veritas Enterprise NetBackup with a StorageTek tape silo.  Our
backups are done in parallel to multiple tape drives, and we back up many
machines at once so these backups are all multiplexed and interleaved.

After weeks of discussion with the vendors, it is starting to look like the
only way to determine the actual number of physical bytes written to tape
has to be determined by backing up one tablespace file repeatedly on one
tape, until the tape fills up, then infer (guesstimate) how many bytes were
written.

The tape drives' hardware can be told to back up files in "native" mode
instead of in "compressed" mode, but one cannot ask them to report how many
bytes were written in "compressed mode" without the tape hardware
"decompressing" the bytes written.

Veritas NetBackup doesn't know how many bytes were written to tape, it can
only report how many bytes the original file had.  It gets its values from
the tape drives.

This took me by surprise, are we the only ones who want to have an exact
reading of how many bytes are written to tape?

[/end rant]

Regards,
Pat.
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