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PL/SQL User's Guide and Reference
10g Release 1 (10.1)

Part Number B10807-01
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LOCK TABLE Statement

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

Oracle has extensive automatic features that allow multiple programs to read and write data simultaneously, while each program sees a consistent view of the data; you should rarely, if ever, need to lock tables yourself.


Description of lock_table_statement.gif follows
Description of the illustration lock_table_statement.gif

Keyword and Parameter Description


A table or view that must be accessible when you execute the LOCK TABLE statement. For the syntax of table_reference, see "DELETE Statement".


The type of lock. It must be one of the following: ROW SHARE, ROW EXCLUSIVE, SHARE UPDATE, SHARE, SHARE ROW EXCLUSIVE, or EXCLUSIVE.


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.


The following statement locks the accts table in shared mode:


Related Topics

COMMIT Statement, ROLLBACK Statement