Re: DBMS Failure Issue

From: Michel Cadot <micadot{at}altern{dot}org>
Date: Sat, 12 Nov 2005 20:02:04 +0100
Message-ID: <43763c2b$0$8296$626a14ce@news.free.fr>

"Leigh Williams" <leighwilliams_at_gmail.com> a écrit dans le message de news: 1131807109.852054.259830_at_g44g2000cwa.googlegroups.com...
| The logwriter writes to the logfile on disk, so it must accumulate a
| block of log records before flushing to the log file. Suppose a
| transaction commits, but the commit record flushing is delayed by the
| log writer waiting to fill a block. What would happen to the
| transaction if DBMS failure occured while waiting for its commit record
| to be flushed? Would it simply be a case of a transaction undo in
| recovery?

|

When a session commits it write a commit marker in the log buffer and signals LGWR to flush the log buffer onto disk *without* waiting the block to be filled. Then the session waits on the "log file sync" event till the block is on the disk. This leads in waste in the log block and you can see the amont of this wastage in the "redo wastage" statistics.

Regards
Michel Cadot Received on Sat Nov 12 2005 - 13:02:04 CST