Re: Chained vs. migrated rows - Any easy way to tell the difference?
Date: Wed, 29 Oct 2008 07:42:06 +1100
You can tell the difference between row migration and chaining by listing the chained rows with ANALYZE table LIST CHAINED ROWS and then fetching the first column from each "chained row" in a single query. The count of continued row fetches will be incremented for every migrated row, but not for most chained rows (unless the first cut point happens to fall with the first column, which should be rare).
@ Regards, @ Steve Adams @ http://www.ixora.com.au/ - For DBAs @ http://www.christianity.net.au/ - For all
Subject: Chained vs. migrated rows - Any easy way to tell the difference? Date: Tue, 28 Oct 2008 15:27:51 -0400
> We have two databases that are showing very high number of/ table fetch
> continued row/ in v$sysstat each day and before doing a move or
> export/import or copying the rows off and reinserting them I was hoping
> to find out if I'd really gain anything.
> All I found in the Oracle docs was the suggestion to assume they're
> migrated and if the fix doesn't work then that means they were really
> chained ( Note:122020.1).
> I'm considering using length() on all the columns and adding them
> together to find any rows that wouldn’t fit in a block but was wondering
> if there was an easier way. Besides, one of the tables (third party
> app) has a long raw column so there's no easy way to get the column
> length there.
> Jay Miller