Help Center/ GaussDB(DWS)/ SQL Syntax Reference/ SQL Syntax Reference (9.1.0.x)/ TCL Syntax/ SET TRANSACTION
Updated on 2025-07-22 GMT+08:00
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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

Set the isolation level and access mode of the transaction. 
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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

Table 1 SET TRANSACTION parameters

Parameter

Description

Value Range

LOCAL

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

-

SESSION

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

A string, which must comply with the naming convention.

ISOLATION LEVEL

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

NOTE:

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.
  • READ COMMITTED: Only committed data is read. The default value is READ COMMITTED.
  • 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 mode or read-only mode.

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;
Parent Topic: TCL Syntax