Re: Asynchronous Commit Feature of 10.2 - Basic Qs

  • From: "Anjo Kolk" <anjo.kolk@xxxxxxxxxxx>
  • To: VIVEK_SHARMA <VIVEK_SHARMA@xxxxxxxxxxx>
  • Date: Fri, 22 Sep 2006 12:07:44 +0200

The answer is YES. Nothing really to clarify. SCNs determine what you see in
a transaction/select. Remember currently Oracle never goes back to the redo
log file to read an SCn as part of the scenario that you describe. It
doesn't even look in the redo log buffer. The only place that is inspected
is the data block, the corresponding undo and the corresponding undo header
(TX table).

Anjo.


On 9/22/06, VIVEK_SHARMA <VIVEK_SHARMA@xxxxxxxxxxx> wrote: 

 Anjo, Folks



If you could possibly Clarify Anjo's reply below?



Also I infer that Anjo reply means "YES" to my Question below (since an
SCN would have been generated by the COMMIT at 10:00)



Qs 3 If multiple processes are running parallely & committing data with a
related logical inter-dependency between them while doing updates, can the

same be maintained when using the Asynchronous commit feature? To Explain
this in simpler words:-



Assume for 1 process COMMIT_WRITE is set to BATCH,NOWAIT.

Assume at 10:00 this process issues a Commit after updating a field value
to say "A".

Assume that Oracle decides to write it to redo logs on Disk at 10:02.



Question - If at 10:01 ANOTHER process reads(SELECTs) the same field
value, will it get the UPDATED field Value of "A"



Anjo's Reply - The redo is only used for recovery. You are confusing the
SCN number. The current SCN and the snapshot scn (start of statement)
dictate what you will see as commited or not.



Thanks indeed


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