Help Center/ Data Warehouse Service/ SQL Syntax Reference/ SQL Syntax Reference (9.1.1.x)/ DDL Syntax/ Connections, Sessions, and Resource Clearing/ CLEAN CONNECTION
Updated on 2026-07-02 GMT+08:00
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CLEAN CONNECTION

Function

CLEAN CONNECTION clears database connections. You may use this statement to delete a specific user's connections to a specified database.

It is mainly used to handle database exceptions, clear idle or invalid connections, and check connection access before dropping a database to prevent operation failures.

Precautions

You must specify either dbname or username.

Syntax

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CLEAN CONNECTION 
    TO { COORDINATOR ( nodename [, ... ] ) | NODE ( nodename [, ... ] )| ALL [ CHECK ] [ FORCE ] }
    [ FOR DATABASE dbname ] 
    [ TO USER username ];

Parameter Description

Table 1 CLEAN CONNECTION parameters

Parameter

Description

Value Range

CHECK

This parameter can be specified only when the node list is specified as TO ALL.

Setting this parameter will check whether a database is accessed by other sessions before its connections are cleared.

If any sessions are detected before DROP DATABASE is executed, an error will be reported and the database will not be deleted.

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FORCE

This parameter can be specified only when the node list is specified as TO ALL.

If this parameter is specified, all threads related to the specified dbname and username will receive the SIGTERM signal and be forcibly closed.

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COORDINATOR ( nodename [, ... ] ) | NODE ( nodename [, ... ] ) | ALL

Deletes connections on a specified node. There are three scenarios:

  1. Deletes connections on a specified CN.
  2. Deletes connections on a specified DN.
  3. Deletes connections on all nodes, including CNs and DNs.

nodename is an existing node name.

dbname

Deletes connections on a specific database.

If this parameter is not specified, connections to all databases will be deleted.

Valid database name.

username

Deletes connections on a specific user.

If this parameter is not specified, connections of all users will be deleted.

Valid username.

Examples

Clean connections to nodes dn1 and dn2 for the template1 database.

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CLEAN CONNECTION TO NODE (dn1,dn2) FOR DATABASE template1;

Clean user jack's connections to dn1.

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CLEAN CONNECTION TO NODE (dn1) TO USER jack;

Delete all connections to the gaussdb database.

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CLEAN CONNECTION TO ALL FORCE FOR DATABASE gaussdb;

FAQs

Failed to Delete a Database and an Error Is Reported Indicating that a Session Is Connected to the Database

Parent Topic: Connections, Sessions, and Resource Clearing