The syntax of lock table is:
lock table table_name in {share | exclusive} mode
[wait [no_of_seconds] | nowait]
The wait/nowait option allows you to specify how long the command waits to acquire a table lock if it is blocked (see “Using the wait/nowait options of the lock table command”).
The following considerations apply to the use of lock table:
lock table can be issued only within a transaction.
You cannot use lock table on system tables.
You can first use lock table to lock a table in share mode, then use it to upgrade the lock to exclusive mode.
You can use separate lock table commands to lock multiple tables within the same transaction.
Once a table lock is obtained, there is no difference between a table locked with lock table and a table locked through lock promotion without the lock table command.
