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Oracle RAM memory usage

That said, what are some of the key indicators of memory efficiency and usage?  Rather than list each metric in a single script, the memsnap.sql script below obtains many key memory metrics in a single query and presents them all at once. 

See Code depot for complete script

 

 select
       buffer_hit_ratio,

       percent_shared_pool_free,
       lib_cache_hit_ratio,
       object_reloads,
       dd_cache_hit_ratio,

. . . .
       latch_miss_ratio
from
(select
       100 -
       100 *
       (round ((sum (decode (name, 'physical reads', value, 0)) -
        sum (decode (name, 'physical reads direct', value, 0)) -
        sum (decode (name,

        'physical reads direct (lob)', value, 0))) /

        (sum (decode (name,

        'session logical reads', value, 1))),3)) buffer_hit_ratio
 from 
       sys.v$sysstat
 where
        name in ('session logical reads',

                 'physical reads direct (lob)',  
                 'physical reads', 'physical reads direct')),
. . .

  from
       v$sysstat a,
       v$sysstat b
 where
       a.name = 'sorts (disk)'
   and b.name = 'sorts (memory)'),
(select
       round(100 * (sum (sys.v$latch.misses) /
       sum (sys.v$latch.gets)),2) latch_miss_ratio
  from
       sys.v$latch),

 

The buffer cache hit ratio  is the first statistic shown in the above script.  As mentioned, many DBAs today maintain that this measure is not a good indicator of performance, but is this actually true?

 


The above is an excerpt from Oracle Performance Troubleshooting by Robin Schumacher.

It's only $19.95 and you can order it and get instant access to the Oracle scripts here:

http://www.rampant-books.com/book_2003_1_perf.htm

 

 

 

 
 
 

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