Archives of the TeradataForum
Message Posted: Mon, 13 Jun 2011 @ 07:21:05 GMT
<-- Anonymously Posted: Monday, June 13, 2011 02:41 -->
Hi Teradata Experts,
Recently, I was reading Teradata manuals to get more info about pseudo tables.
The information I could gather is: Since Teradata distributes a table across all amps, it is possible (without the pseudo table mechanism employed) that one process would grab a lock on a table on one amp and a different process grabs a lock on the same table on a different amp. They would both be trying to grab a full lock and neither could get it because the other holds out a lock that is needed. Therefore, in order to avoid this deadlock situation, one amp effectively serves as the starting amp (see the physical implementation class or the Teradata manuals for information on how) for all locks on the table and this is called a "Pseudo Table lock". Like a semaphore, it prevents deadlock on the locking of a table. Once a process has a pseudo lock, it can lock the table on all amps.
For BATCHUSER of my current project: When I try to submit insert statement from two different sessions, it results in DEADLOCK.
Thanks in advance for all your help.
|Copyright 2016 - All Rights Reserved|
|Last Modified: 27 Dec 2016|