Re: HOW TO FIGURE OUT SUITABLE INITRANS VALUE FOR A TABLE

Hi!

Btw, minimum inittrans is 2 in 9i when block is formatted using conventional insert and it's 3 when a block is formatted using direct path insert, even though data dictionary claims otherwise.

Optimal inittrans for a *block* is the number of concurrent transactions in it. Optimal inittrans for a segment should be set such way that majority of the blocks shouldn't have the need to extend ITL area during transaction activity in them. That means, if 99% of your blocks experience 2 concurrent transactions at a given time, but 1% have 4 transactions, then I'd still set inittrans to 2, but maxtrans to higher value instead.

It is hard to calculate the number of concurrent transactions in a block, since we don't have much control in which blocks our data is stored, nor we don't know which exact rows will be modified in given time that well either. One common pitfall is a recommendation to set inittrans for table as high as many concurrent inserts to it you have -> this may lead into overly large ITLs, because if using multiple freelists and freelist groups, inserts are spread into several blocks anyway.

An easy for smapling optimal inittrans for existing data is to use "alter system dump datafile" command to dump a range of datablocks and grep for "itc:" from the file, this shows you max interested transaction count for evey block.

Tanel.

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Thursday, September 25, 2003 1:13 PM

> Tables have default INITRANS value.
> I want to set this parameter to a suitable value. Because INITRANS is 1 as
default value and I want to avoid from load of dynamic
> But how can I figure out suitable value of this parameter for each table.
>
>
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Please see the official ORACLE-L FAQ: http://www.orafaq.net
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Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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