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Unanswered: re: update statement
what are the different techniques that one can use
to decrease the overall time it takes to do
update of a large table ....... ?????
thanks for your replies
On large updates, you should have a good eye on your rollback segment.
You can create a large rollback segment and issue your update statement after the statement:
set transaction use rollback segment <large rollback segment>
You can update the table part by part with the help of your primary key field, like
where pk between 1 and 100000
where pk between 100000 and 200000
and a commit in between so that your rollback segment wont get eaten up.
You can write a small PL/SQL to do the above using cursors and a commit in between.
there are many other ways.
Some things which may help
1) If your subquery is using a correlated subquery then check to see if it is using an index as this may make a big difference (depending on the number of rows in the associated tables).
2) Check your table are analyzed.
3) Updates may cause row chaining so it is a good idea to check your pctfree. It might be worthwhile using alter table move to alter this value.
4) Bulk binds can also make a big difference if your using plsql to do your update.