READ_ISOLATION_LEVEL=

READ_ISOLATION_LEVEL=

Specifies the level of isolation from other table users that is required during SAS/ACCESS read operations.

Default value: None

Syntax
Details

Syntax

READ_ISOLATION_LEVEL= ACCESS|READ|WRITE

ACCESS

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

Effect: Permits other users to obtain a lock on the table or view.

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. It does not prevent other users from reading the object.

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. It is released only when the table is closed.

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

Details

Specifying ACCESS can return inconsistent or unusual results. And, specifying WRITE is unnecessarily restrictive, locking the entire table until the read operation is finished. You cannot explicitly release a WRITE lock. It is only released when the DBMS object on which it is applied is closed. Therefore, whenever possible specify READ; it is usually adequate for most SAS/ACCESS processing.

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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