Re: Determine sequence cache size in RAC

• Original Message -----
  ]From: "CRISLER, JON A (ATTCORP)" <JC1706_at_att.com>
  ]To: <denis.sun_at_yahoo.com>; <oracle-l_at_freelists.org>
  ]Sent: Monday, May 02, 2011 11:14 PM
  ]Subject: RE: Determine sequence cache size in RAC
  ]
  

]Values of 1000 to 10000 have worked well for me :) This was derived from trial
and error.
]

That makes sense.

Each index entry will take about 15 or 16 bytes - giving about 520 entries per index leaf block.

A side effect of RAC means that the index leaf blocks will be doing 50/50 splits leaving you with about 260 entries per block.

This means at a cache size of 1,000 an instance will fill about 4 leaf blocks before refreshing the cache and colliding briefly on the top leaf block with the previous instance holding the highest cache value. At a cache size of 10,000 that will be about 40 blocks for an instance before a collision.

The more instances you have, the larger the cache needs to be.

Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

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