As RAM storage becomes cheaper than ever, many companies are
exploring the issue of fully-cached Oracle databases. As I noted
in an earlier Oracle tip, solid-state disk is changing the way that
Oracle professionals and manage and tune their databases.
http://www.dba-oracle.com/oracle_tips_SSD.htm
One of the issues is the relatively high-cost of fetching an Oracle
data block from disk. In theory RAM is 10,000 times faster than
disk milliseconds vs. nanoseconds), but when you add-in the overhead of
lock serialization and latches, a logical I/O might be less than a
thousand times faster than a "physical" disk I/O.
In an article in IT-director.com they note a new company called
InfoCyclone that recognizes the kludgy block-based approach to Oracle
RAM I/O.
http://www.it-director.com/article.php?articleid=11729
This tool detects frequently-referenced data and caches it is it's
high-speed version of the Oracle data buffer. According to the
article:
"You might ask why you shouldn't use Oracle's caching. Well, you
could. But Oracle effectively treats a cache as a sort of
memory-oriented disk: it still uses a block-based approach, you have to
check whether the data you want is on disk or in cache, you have to
check with the cache is clean or dirty, and so on. All of which incurs
an overhead that InfoCyclone avoids."
We also see companies such as Texas Memory Systems offering
solid-state disk replacement for the Oracle data buffer cache to
speed-up I/O at the physical level:
http://www.texmemsys.com/files/f000139.pdf
Still, we see some companies such as UNISYS getting blistering
performance from Oracle (on Windows, no less) using 100 gigabyte
db_cache_size and db_keep_cache_size:
http://www.dba-oracle.com/oracle_tips_10g_windows.htm
Got scripts?
Mike
Ault, one of the world's most widely-read Oracle experts, has finally consented to
release his complete collection of more than 450 Oracle scripts,
covering every possible area of Oracle administration and management.
Mike has priced his
collection of 465 scripts at $39.95, less than a dime per script. You
can download them immediately at this link:
http://www.rampant-books.com/download_adv_mon_tuning.htm
|
