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Message Posted: Wed, 28 Mar 2007 @ 10:19:49 GMT
<-- Anonymously Posted: Tuesday, March 27, 2007 18:51 -->
To avoid deadlocks initially Teradata obtains requested lock on a pseudo table then applies the actual lock when it executes that particular step.
For example if we have two different transactions which are trying to access the same table t1.
Txn 1 --- read lock on t1 Txn 2 --- write lock on t1
In older system (before pseudo lock feature) assume that couple of amps will obtain read lock on t1 and remaining amps obtain write lock on t1. In such situtaion deadlock will occur and one of the transaction needs to be aborted to complete the other. To avoid such situations lock on pseudo table has to be applied before locking the actual table.
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