Big tables

[Watt, Peter]

Depending on what you are modifying in the table, dropping the indexes may
not be all that much help.  RDB takes a big hit whenever you change an index
value but relatively nothing if you are not modifying index values.  As
well, the cost of re-adding the index after you are finished must be
enormous!  

The are multiple options you can explore.  If you have multiple cpu's on
your box, breaking up the processing will help immensely.  Yes, putting it
into sql scripts may speed it up marginally but for the length of your
process, this may be significant.  Try some trial runs with different
'commit' rates.  You may find that doing a commit after every 5000 rows is
more efficient than after 20000.  If you must unload your table to modify
it, split it across multiple drives and create multiple processes to perform
the update.

Hope this helps.  If you could provide a little more background, I may be
able to suggest few more alternatives.

Regards,
Peter Watt

	-----Original Message-----
	From:	l.dyer@mgn.co.uk [SMTP:l.dyer@mgn.co.uk]
	Sent:	Monday, March 22, 1999 5:46 AM
	To:	powerh-l@lists.swau.edu
	Subject:	Big tables




	We have an Rdb database on VMS (Powerhouse 710g1) that contains only
one
	table. This table contains some 48,000,000 records which we wish to
update
	in a timely fashion.

	We have dropped all the indexes and are proceeding to update with
QTP.

	We obviously have the option of running an SQL script if necessary.

	I realise that we can use RMU to create a flat file which we can
update and
	reload, but I am not sure that this will significantly reduce
running time.

	Does anyone have any comments on the above alternatives or any other
	methods that may significantky reduce update time.

	Lynden


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