PL/SQL User's Guide and Reference

LOCK TABLE Statement

Description

The LOCK TABLE statement lets you lock entire database tables in a specified lock mode so that you can share or deny access to tables while maintaining their integrity. For more information, see "Using LOCK TABLE"

Syntax

lock_table_statement ::=

LOCK TABLE table_reference[, table_reference]...
   IN lock_mode MODE [NOWAIT];

table_reference ::=

[schema_name.]{table_name | view_name}[@dblink_name]

Keyword and Parameter Description

table_reference

This identifies a table or view that must be accessible when you execute the LOCK TABLE statement.

lock_mode

This parameter specifies the lock mode. It must be one of the following: ROW SHARE, ROW EXCLUSIVE, SHARE UPDATE, SHARE, SHARE ROW EXCLUSIVE, or EXCLUSIVE.

NOWAIT

This optional keyword tells Oracle not to wait if the table has been locked by another user. Control is immediately returned to your program, so it can do other work before trying again to acquire the lock.

Usage Notes

If you omit the keyword NOWAIT, Oracle waits until the table is available; the wait has no set limit. Table locks are released when your transaction issues a commit or rollback.

A table lock never keeps other users from querying a table, and a query never acquires a table lock.

If your program includes SQL locking statements, make sure the Oracle users requesting locks have the privileges needed to obtain the locks. Your DBA can lock any table. Other users can lock tables they own or tables for which they have a privilege, such as SELECT, INSERT, UPDATE, or DELETE.

Example

The following statement locks the accts table in shared mode:

LOCK TABLE accts IN SHARE MODE;