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Archives of the TeradataForum
Message Posted: Mon, 27 Nov 2012 @ 00:23:02 GMT
| Subj: | | Re: Access Logging - Impact on performance |
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| From: | | Ruth Fenwick |
I agree with the other comments that ODBC will be a slow way to load your data, but I have to disagree that access logging is a small cost.
Even if you were loading via a more efficient TPUMP load strategy, the impact of access logging will be significant on any operation that is based
on 1 row at a time doing many, many inserts from the same session.
DBC.AccLogTbl (the underlying table for accesslog), is a SET table with a PRIMARY INDEX of ( LogonDate ,LogonTime ). Think about the impact
of inserting a million rows into a table that all have the same primary index value. AccessLog will be so skewed on that value, that DBC may run
out of space on that AMP. And the processing will slow down as each row into DBC.AccLogTbl will need to be checked for duplicates, by the time
you get to 100,000 rows, your load will begin to grind to a halt (assuming DBC hasn't run out of space first).
AcessLogging should be turned off or only on for select for databases that will have high volume inserts, regardless of the load mechanism.
It should be off for any high volume tactical application as well.
Ruth Fenwick
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