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Instance Recovery Question

From: AJG <noemail_at_noemail.noemail>
Date: 3 Dec 1998 05:12:08 GMT
Message-ID: <36661AD3.891C007F@noemail.noemail>


Hi,

I was training a new DBA on how Oracle handles recovery from instance failure (i.e., roll forward, roll back), and I came across this unusual little scenario that I am unclear on:

A change is made to a data block
That change is recorded in a rollback block Change also recorded in log buffer
DBWR writes data block to disk
Instance crashes
- Change in log buffer not written to disk yet

Two Solutions:
1) Oracle always writes out the rollback block before the changed data block.
2) Oracle always waits to flush a change in log buffer to disk before writting the changed block (data or rollback)

2 sounds unlikely to me, so I'm going with 1.

I'm I correct?

Thanks!

Alan.

--
Alan Gano
http://home.att.net/~alangano/index.html Received on Wed Dec 02 1998 - 23:12:08 CST

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