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Oracle Data Block Size [message #65534] Tue, 19 October 2004 03:15 Go to next message
Messages: 105
Registered: February 2004
Senior Member
Dear frends,

I am Confusing in Oracle DATA Block size in Database.

I have few question regarding sizing

1.What are the factors which I have to consider before sizing the Oracle data block ?
2.What should be Oracle Block Size for DSS system? and most important why ??
3.What should be the Oracle Block size for OLTP system ? and most important why ??
4.How can i see the Buffer cache size in Unix ? and Most important How can i change it?

I am unable to find the proper answer of these questions .. Pl. let me know proper answer of above questions..

It will be big thax for answer!!!!!!!!!!

Re: Oracle Data Block Size [message #65579 is a reply to message #65534] Tue, 02 November 2004 00:03 Go to previous message
Messages: 269
Registered: November 2000
Senior Member
Balance db_block_size with Operating System Block Size.
For good performance Oracle Block size should be made equal to or a multiple of the O/S blocksize. It is not sensible to have

the size
SMALLER than the OS blocksize as a single read will actually read in 'OS block size bytes' even if only part of this is

passed on to Oracle.

Oracle recommend 4 - 8k for OLTP, while 16K for Data warehouse systems.

Usually for OLTP (Online Transaction Processing) systems is advisable to have smaller block size assuming that data

requirement for information tend to be small and granular (Not every process is using the same information of the same


Contrary, for DSS (Decision Support Systems) were reads tend to be large, a bigger database block size will help in caching

more information in memory with less I/O accesses.
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