SET TRANSACTION

Function

SET TRANSACTION sets the characteristics of the current transaction. It has no effect on any subsequent transactions. Available transaction characteristics include the transaction separation level and transaction access mode (read/write or read only).

Precautions

None

Syntax

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{ SET [ LOCAL ] TRANSACTION|SET SESSION CHARACTERISTICS AS TRANSACTION }
  { ISOLATION LEVEL { READ COMMITTED | READ UNCOMMITTED | SERIALIZABLE | REPEATABLE READ }
  | { READ WRITE | READ ONLY } } [, ...]

Parameter Description

• LOCAL

  Indicates that the specified command takes effect only for the current transaction.

• SESSION

  Indicates that the specified parameters take effect for the current session.

  Value range: a string. It must comply with the naming convention.

• ISOLATION_LEVEL_CLAUSE
  Specifies the transaction isolation level that determines the data that a transaction can view if other concurrent transactions exist.

  

  • The isolation level of a transaction cannot be reset after the first clause (INSERT, DELETE, UPDATE, FETCH, COPY) for modifying data is executed in the transaction.

  Valid value:

  • READ COMMITTED: Only committed data is read. This is the default.
  • READ UNCOMMITTED: GaussDB(DWS) does not support READ UNCOMMITTED. If READ UNCOMMITTED is set, READ COMMITTED is executed instead.
  • REPEATABLE READ: Only the data committed before transaction start is read. Uncommitted data or data committed in other concurrent transactions cannot be read.
  • SERIALIZABLE: GaussDB(DWS) does not support SERIALIZABLE. If SERIALIZABLE is set, REPEATABLE READ is executed instead.
• READ WRITE | READ ONLY

  Specifies the transaction access mode (read/write or read only).

Examples

Set the isolation level of the current transaction to READ COMMITTED and the access mode to READ ONLY.

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START TRANSACTION;
SET LOCAL TRANSACTION ISOLATION LEVEL READ COMMITTED READ ONLY;
COMMIT;