Locked Space

What is meant by locked space? Describe locking concepts?

Questions by sha.vin1987

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vjjammi

  • Aug 25th, 2010
 

DB2 Supports Locking mechanism at three levels.

1. Space Level.
2. Table Level.
3. Page Level.

The above hierarchy has some significance and in order to lock a page at the higher level, you needn't lock any other elements at the lower level. But if you wanna lock at the lower level, you should have locks at the related higher level also.
Example : In order to lock a page, you have to lock the table space also.

Locks enable two things.

1. Reading of Data
2. Updating of Data

Types of TableSpace and table Locks.

------------------------------------------------------------------
S.No  Type                    Access                    Access
                                   Required              For others
----------------------------------------------------------------
1.     Share                   Read Only              Read Only
2.     Update                Read with an          Read Only 
                                    intent to update
3.     Exclusive               Update                  No Access
4.     INTENT Share        Read Only             Update      
5.     INTENT Exclusive   Update                  Update
6.     Share Intent Excl.  Read or update     Read only

Types of Page Locks

------------------------------------------------------------------
S.No  Type                    Access                    Access
                                   Required              For others
----------------------------------------------------------------
1.     Share                   Read Only              Read Only
2.     Update                Read with an          Read Only 
                                    intent to update
3.    Exclusive               Update                   No Access


 

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