Hi Jeff,

We ran on unload-load on a 46GB database a few months back. The database was 
>90% utilised before the unload-load and 52% afterwards. Besides the obvious 
benefit of significantly reducing the database size, we have also seen better 
performance, particularly with database backups.

That's the good news. The bad news is that all up our server was off the air 
for around 24 hours. And that was with playing a few tricks. We normally run 
the database with *SM mirroring enabled. We split the mirrors and used one set 
for the unload and one set for the load. This also gave us an easy backout path 
without having to restore the database. We then forced our 3590 tape drives to 
write in uncompressed mode with resulted in multiple tapes being need to write 
the unload data. The advantage here is that as soon as one tape was full, the 
unload would start writing to the 2nd tape and we could use the first tape to 
start the load. So even though the unload took just under 16 hours we were able 
to start the load after only 6 hours. The load took 17.5 hours. Note that the 
unload-load utilities do not support automatic tape libraries so we also had to 
run the 3590s, which are in a 3494 library, in manual mode.

The unload-load ran on a 4-way RS/6000 R50 with 512MB memory, SSA disks, AIX 
4.3.2 and TSM 3.7.3.6.


regards,

Trevor