Ben said:
I have several Dell PE6650's running Win2K Server in a
RAID5 configuration. A couple of these servers host a
huge Oracle database and we are experiencing performance
issues. The DBA suggests enabling write caching for
troubleshooting purposes but when I get to that option in
the disk properties, the option is dimmed out so that I
cannot enable.
Can anyone tell me how to un-dim this option so that I can
enable write caching?
Thanks, Ben
While I can't help you enable the write cache option, I have had more than
just a bit of experience with Oracle databases. Some of the more immediate
suggestions (and I'm sure you've already tweaked some of them):
* Use RAID 1 instead of RAID 5. The performance is much better.
* Do some experimentation with DB_BLOCK_SIZE (if you have a spare machine)
to find the sweet spot for your disk drives' formatted allocation size.
(There's actually a formula and some methodology you can use, but I don't
have it available right now.)
* Ensure your SHARED_POOL_SIZE and DB_BLOCK_BUFFERS is large enough,
especially the SHARED_POOL_SIZE. If SHARED_POOL_SIZE is too low, you won't
get the full advantage of your DB_BLOCK_BUFFERS.
* Set SHARED_POOL_RESERVED_SIZE and SHARED_POOL_MIN_ALLOCATION to get those
large requests into a less fragmented section of memory.
* For your static data - the stuff that doesn't get updated much (read
mostly) - use the CACHE parameter to pin the data in memory.
* If you have some intimate knowledge of the database application, group the
tables and indexes into separate tablespaces and store the tablespaces on
logically and physically separate drives to reduce I/O contention.
The biggest performance gain will come from this next one ...
* Shoot the programmer for not taking the time to TKPROF and optimize the
SQL statements.
(There is only so much the SysAdmin or DBA/DBM can do. More often than not,
it is the programmers that mess up performance.)
