Tag Archives: Range locks

RangeX-X Key-Range Locks in SERIALIZABLE isolation level (part 3)

Posted by yrushka on June 10, 2011 None comments

I will continue in this part describing other types of Key – Range locks: RangeX-X combined with RangeS-U locks.

As a reference I will use the same table created in part 1 – range_lock.

RangeX-X Locks

RangeX-X locks are exclusive resource locks acquired on Index key values from a specific range when the transaction modifies a key value from the Index. The locks are exclusive locks… Continue reading

RangeS-U – Key-Range Locks in SERIALIZABLE isolation level – (part 2)

Posted by yrushka on May 30, 2011 None comments

I will continue in this part describing other types of Key – Range locks.

As a reference I will use the same table created in part 1 – range_lock.

RangeS-U Locks

RangeS-U locks are locks acquired on Index key values from a specific range when the following conditions are met:

  • The transaction contains an UPDATE statement
  • WHERE clause is used to specify a condition
Continue reading

RangeS-S – Key-Range Locks in SERIALIZABLE isolation level (part 1)

Posted by yrushka on May 25, 2011 1 comments

Overview
 

Locking mechanism in SQL is by far one of the most complex mechanism and hard to explain. Blockages and Locks are a DBA’s daily problems when confronting with concurrent processes which access same records of the same table. In order to have a high – performance system, a very important aspect to consider is isolation of concurrent operations. In high-activity systems like web-sites, ERP’s or online shops… Continue reading