Monday, December 15, 2008

concurrency related problems and control - Isolation levels

concurrency related problems


1-dirty read
2-Nonrepeatable read

3-lost data

4-phantom read

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concurrency control

1-Pessimistic Control.

(SQL Server locks the resource until user performs the action she/he needs and then release for others.)


1/1- Read Uncommitted Isolation Level

1/2- Read Committed Isolation Level

1/3- Repeatable Read Isolation Level

1/4- Serializable Isolation Level


2-Optimistic Control.

(SQL Server does not hold locks but once read, check for inconsistency for next read.)


2/1- Snapshot Isolation Level

2/2- Read Committed Snapshot Isolation Level


1 comment:

花蓮民宿黃頁 said...
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