TABLE 8 . 2 Table Lock Modes
ROW SHARE ：Permits concurrent access to the locked table, but prohibits other
users from locking the entire table for exclusive access.
ROW EXCLUSIVE ：Same as ROW SHARE, but also prohibits locking in SHARE mode. This type
of lock is obtained automatically with standard DML commands such
as UPDATE, INSERT, or DELETE.
SHARE ：Permits concurrent queries but prohibits updates to the table; this
mode is required to create an index on a table and is automatically
obtained when using the CREATE INDEX statement.
SHARE ROW EXCLUSIVE ： Used to query a whole table and to allow other users to query the
table, but to prevent other users from locking the table in SHARE mode
or updating rows.
EXCLUSIVE ：The most restrictive locking mode; permits queries on the locked table
but prohibits any DML by any other users. This mode is required to
drop the table and is automatically obtained when using the DROP
TABLE statement.
monitor lock view：v$session,v$transaction,v$lock,v$locked_object
