UPDATE_ISOLATION_LEVEL=

UPDATE_ISOLATION_LEVEL=

Specifies the level of isolation from other table users that is required as SAS/ACCESS reads Teradata rows in preparation for updating the rows.

Default value: None

Syntax
Details

Syntax

UPDATE_ISOLATION_LEVEL= ACCESS|READ|WRITE

ACCESS

obtains an ACCESS lock by ignoring other users' ACCESS, READ and WRITE locks.

READ

obtains a READ lock if no other user holds a WRITE or EXCLUSIVE lock.

Effect: prevents other users from being granted a WRITE or EXCLUSIVE lock.

WRITE

obtains a WRITE lock on the table or view if no other user has a READ, WRITE, or EXCLUSIVE lock on the resource. You cannot explicitly release a WRITE lock. A WRITE lock is released only when the DBMS object on which it is applied is closed.

Effect: Prevents other users from obtaining any lock but ACCESS.

Details

The READ value locks the entire table or view, allowing other users to acquire READ locks. The READ value can lead to deadlock situations.

The WRITE value prevents other users, except those with ACCESS locks, from accessing the table. Although a WRITE value prevents the possibility of a deadlock, it limits concurrent use of the table.

Avoid an ACCESS lock for update if there is a possibility that a different user might update the table at the same time. In this situation, the data can be corrupted.

Use SAS/ACCESS locking options only when Teradata's standard locking is undesirable. For more information, see the LOCKING modifier in your Teradata SQL Reference manual, as well as Understanding the Scope of SAS/ACCESS Lock Options.

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