Answer Posted / mahesh reddy g
lockmodes:
EXCLUSIVE
SHARE
ROW EXCLUSIVE
SHARE ROW EXCLUSIVE
ROW SHARE* | SHARE UPDATE*If NOWAIT is omitted Oracle
will wait until the table is available.
Several tables can be locked with a single command -
separate with commas
e.g. LOCK TABLE table1,table2,table3 IN ROW EXCLUSIVE MODE;
Default Locking Behaviour
A pure SELECT will not lock any rows.
INSERT, UPDATE or DELETE's - will place a ROW EXCLUSIVE
lock.
SELECT...FROM...FOR UPDATE NOWAIT - will place a ROW
EXCLUSIVE lock.
Multiple Locks on the same rows with LOCK TABLE
Even when a row is locked you can always perform a SELECT
(because SELECT does not lock any rows) in addition to
this, each type of lock will allow additional locks to be
granted as follows.
ROW SHARE = Allow ROW EXCLUSIVE or ROW SHARE or SHARE locks
to be granted to the locked rows.
ROW EXCLUSIVE = Allow ROW EXCLUSIVE or ROW SHARE locks to
be granted to the locked rows.
SHARE ROW EXCLUSIVE = Allow ROW SHARE locks to be granted
to the locked rows.
SHARE = Allow ROW SHARE or SHARE locks to be granted to the
locked rows.
EXCLUSIVE = Allow SELECT queries only
Although it is valid to place more than one lock on a row,
UPDATES and DELETE's may still cause a wait if a
conflicting row lock is held by another transaction.
* = Oracle 6 option included for compatibility
| Is This Answer Correct ? | 30 Yes | 14 No |
Post New Answer View All Answers
how can we know the number of days between two given dates using mysql? : Sql dba
what are all types of user defined functions? : Sql dba
Define concurrency control. : Transact sql
what is the difference between ereg_replace() and eregi_replace()? : Sql dba
What is a function in oracle pl sql?
What does dml mean?
What is graph sql?
What is pl sql script?
What are tables and fields in the database?
What is rtm stands for?
How to start oracle sql developer?
When sql appeared?
what is the difference between undefined value and null value? : Sql dba
Will truncate release space?
How to run pl/sql statements in sql*plus?
