Table Level Lock Modes

What are the differences among these table level lock modes - IN SHARE MODE, IN SHARE UPDATE MODE, IN EXCLUSIVE MODE ?

kranthi.kunta
Profile Answers by kranthi.kunta Questions by kranthi.kunta
Jul 9th, 2008
3
3111

Questions by kranthi.kunta answers by kranthi.kunta

Showing Answers 1 - 3 of 3 Answers

Pintu_unix
Profile Answers by Pintu_unix

Jul 20th, 2008

SHARE UPDATE EXCLUSIVE
This mode protects a table against concurrent schema changes and VACUUM runs. Acquired by VACUUM (without FULL), ANALYZE, and CREATE INDEX CONCURRENTLY

EXCLUSIVE
This mode allows only concurrent ACCESS SHARE locks, i.e., only reads from the table can proceed in parallel with a transaction holding this lock mode. This lock mode is not automatically acquired on user tables by any PostgreSQL command. However it is acquired on certain system catalogs in some operations.

SHARE
This mode protects a table against concurrent data changes. Acquired by CREATE INDEX (without CONCURRENTLY).