Jeff,

Maximum value for BUFPOOLSIZE is limited to available virtual memory size.
IBM recommends setting it to 10% of physical memory. I have turned
SELFTUNEBUFPOOLSIZE variable on so that if cache hit ratio decreases by 98%
TSM adjusts BUFPOOLSIZE dynamically. This variable is available in TSM 3.7
and up. Did you monitored cache-hit ratio? How much down it went? How much
physical memory your ADSM server has? Did you setup paging space of equal
size?

We are using shark system for database. Basically shark system contains SSA
Arrays in RAID5 configuration. More than that it has cache of 6GB, which
keeps recently used persistent pages in cache and that gives excellent I/O
rate for frequently used files e.g. Database.

Only database access is not a performance bottleneck. Since you are backing
up 300 client on single server, you should consider splitting up ADSM into
multiple TSM servers.

Bandu