|Oracle9i SQL Reference
Release 2 (9.2)
Part Number A96540-01
SQL Statements: DROP SEQUENCE to ROLLBACK, 14 of 19
TABLE statement to lock one or more tables (or table partitions or subpartitions) in a specified mode. This lock manually overrides automatic locking and permits or denies access to a table or view by other users for the duration of your operation.
Some forms of locks can be placed on the same table at the same time. Other locks allow only one lock for a table.
A locked table remains locked until you either commit your transaction or roll it back, either entirely or to a savepoint before you locked the table.
A lock never prevents other users from querying the table. A query never places a lock on a table. Readers never block writers and writers never block readers.
The table or view must be in your own schema or you must have the
TABLE system privilege, or you must have any object privilege on the table or view.
Specify the schema containing the table or view. If you omit
schema, then Oracle assumes the table or view is in your own schema.
Specify the name of the table to be locked.
If you specify
view, then Oracle locks the view's base tables.
If you specify
subpartition), then Oracle first acquires an implicit lock on the table. The table lock is the same as the lock you specify for
subpartition, with two exceptions:
SHARElock for the subpartition, then Oracle acquires an implicit
SHARElock on the table.
EXCLUSIVElock for the subpartition, then Oracle acquires an implicit
EXCLUSIVElock on the table.
If you specify
table is composite-partitioned, then Oracle acquires locks on all the subpartitions of
Restriction on locking tables: If
table is part of a hierarchy, then it must be the root of the hierarchy.
Specify a database link to a remote Oracle database where the table or view is located. You can lock tables and views on a remote database only if you are using Oracle's distributed functionality. All tables locked by a
TABLE statement must be on the same database.
If you omit
dblink, then Oracle assumes the table or view is on the local database.
"Referring to Objects in Remote Databases" for information on specifying database links
Specify one of the following modes:
SHARE permits concurrent access to the locked table, but prohibits users from locking the entire table for exclusive access.
SHARE is synonymous with
UPDATE, which is included for compatibility with earlier versions of Oracle.
EXCLUSIVE is the same as
SHARE, but also prohibits locking in
EXCLUSIVE locks are automatically obtained when updating, inserting, or deleting.
SHARE permits concurrent queries but prohibits updates to the locked table.
EXCLUSIVE is used to look at a whole table and to allow others to look at rows in the table but to prohibit others from locking the table in
SHARE mode or updating rows.
EXCLUSIVE permits queries on the locked table but prohibits any other activity on it.
NOWAIT if you want Oracle to return control to you immediately if the specified table (or specified partition or subpartition) is already locked by another user. In this case, Oracle returns a message indicating that the table, partition, or subpartition is already locked by another user.
If you omit this clause, then Oracle waits until the table is available, locks it, and returns control to you.
The following statement locks the
employees table in exclusive mode, but does not wait if another user already has locked the table:
The following statement locks the remote
accounts table that is accessible through the database link