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by Craig Shallahamer Get the book here |
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Craig Shallahamer's Blog
The text below is an except from the book, Oracle Performance Firefighting, written by Craig Shallahamer of OraPub, Inc. Figures and tables are not included on this page, only their reference. To order the book in either print or PDF form, click here. ©2009, 2010 by Craig Shallahamer. This is copyrighted material. Please—Out of respect for those involved in the creation of the book and also for their familes, we ask you to respect the copyright both in intent and deed. Thank you. ------------------------------- Another name for relational control is lock management. For example, when the command lock table employee exclusive is issued, that's relational control. Locks prevent an inappropriate change from occurring. When an Oracle process is waiting for a lock, it posts an enqueue wait. I like to say using enqueues is very mature and boring because they are orderly, structured, and just not a lot of fun. (You'll see that latches are just the opposite.) The two broad locking areas are application locks and data dictionary locks. Locking the employee table is an application lock example. Application locks are under the control of application developers. They write the code to issue the locks. On the other hand, data dictionary locks are under the control of Oracle kernel code developers. Please—Out of respect for those involved in the creation of the book and also for their familes, we ask you to respect the copyright both in intent and deed. Thank you. |
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