RE: Secret maximum for INITRANS?

Robert,

I guess you are looking in 'itc' in block dumps which shows the ITL Count.

And yes.. There is an upper bound for number of ITLs based on the block size.
The transaction slots (and other headers) can not use the more than 50% of the
space available for data in the data block. Each ITL will take 24 bytes of space
in variable header part of the data block.

In 2K block (2048) 50 % is 1024 Bytes. In this we can not use the first 48 bytes
(fixed headers in cache layer and TX data layers uses them. So the space
available
for ITLs will be 976 bytes.

So you can get round (976/24) ~41 ITL slots for 2K block size. If you set INITRANS
more than 41 they are simply ignored and only 41 ITLS are created in that block.

Best Regards,
K Gopalakrishnan
Bangalore, INDIA

-----Original Message-----
Eskridge
Sent: Monday, March 04, 2002 4:08 PM
To: Multiple recipients of list ORACLE-L

I'm still messing with my enqueue waits on an insert. I'm now able to recreate it on a test database by throwing enough simultaneous inserts at my table. I was going to make sure which of the tables/indexes was actually causing the waits by individually raising the INITRANS above what they would naturally expand to, and see how the waiting sessions responded.

I was hitting it with 50 simultaneous inserts and usually had 10 sessions go into an enqueue wait until the 40 sessions committed or rolled back. So I was going though the indexes and then tables raising the INITRANS to 50 to see which one(s) made a difference. None of them made a difference.

So I dumped blocks that had been populated only during this exercise. Invariably, there were 0x29 Itl slots. Is there something out there that would limit the Itl entries to 41 even when MAXTRANS=255? Is there some secret bound based on block size? Ours is 2k (which I figure is part of the problem).

Other vital stats: 8.0.5 on Solaris 2.7.

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Author: Robert Eskridge
  INET: bryny_at_dfweahs.net

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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: K Gopalakrishnan
  INET: kaygopal_at_yahoo.com

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