ITL Waits and row migration.

Oracle Version 11.2.0.3 PSU3
OS: SLES11 GA 64 bit
We had an issue with ITL waits on a specific table. In test this resulted in a deadlock so as a fix we rebuilt the table with initrans 8 and pctfree 75, this has improved the situation as we no longer have deadlocks but we have had an instance of high waits for ITL slots. Our development team assure us that a maximum of 6 transactions should be active on the table in question at any given time so we should not see any waits at all. As a bonus feature the table in question is initially loaded with just the primary key columns and the rest of the data (60 columns in all) is filled in over time which can cause considerable row migration to occur has anyone else encountered an issue of this type? Does row migration use additional ITL slots? I am attempting to replicate this in a development environment but so far can not get a replication of the problem.

rp0428 wrote:
Row migration can consume excess ITL entries - every row migrated in a single transaction will allocate an ITL slot in the target block, so if you manage to get (say) 5 rows in a block migrating in a single transaction and they all migrate to the same block you will find that you have used 5 ITL slots in that block - so you can't rule out the possibility that the migration is the cause of the ITL waits.
Can you expand on that a bit and reconcile it with what you say in the ITL entry in your Oracle Scratchpad Glossary article?
http://jonathanlewis.wordpress.com/2009/06/23/glossary/
The transaction needs to acquire only one ITL entry in the block no matter how many rows in the block it changes.
If an ITL (Interested Transaction List) entry represents 'interest' by a singlel transaction why would that single transaction need more than one entry in the block when migrating rows but not when updating existing rows?
What am I overlooking?
rp0428,
There are two possible replies to that question - the absolutely straightforward one is that I forgot to mention any special cases (the "Index Explosion" bug is another, very similar, case) when I wrote that note; the "wiggle" one is that each migration event behaves like a recursive transaction, which leaves you with one ITL entry per arriving row.
Regards
Jonathan Lewis

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(Sorry for my bad english)
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public class Buffer{
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ITL Waits and row migration.

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