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Manual Locking and User-Defined Locks- Locking and Latching
So far, we have looked mostly at locks that Oracle places for us transparently. When we update a table, Oracle places a TM lock on…
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Setting Up for the Test- Locking and Latching
In order to test, we’ll need a schema (set of tables) to work with. We’ll be testing with multiple users and want to measure the…
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Latches- Locking and Latching
Latches are lightweight serialization devices used to coordinate multiuser access to shared data structures, objects, and files. Latches are locks designed to be held for…
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DDL Locks- Locking and Latching-2
A view that is invaluable for looking at this information is DBA_DDL_LOCKS. There is no V$ view. The DBA_DDL_LOCKS view is built on the more…
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Latch “Spinning”- Locking and Latching
One thing I’d like to drive home with regard to latches is this: latches are a type of lock, locks are serialization devices, and serialization…
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Blocked Merges, Updates, and Deletes- Locking and Latching-1
In an interactive application—one where you query some data out of the database, allow an end user to manipulate it, and then put it back…
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Optimistic or Pessimistic Locking? – Locking and Latching
So which method is best? In my experience, pessimistic locking works very well in Oracle (but perhaps not so well in other databases) and has…
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Blocked Inserts- Locking and Latching
There are a few times when an INSERT will block. The most common scenario is when you have a table with a primary key or…
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Blocked Merges, Updates, and Deletes- Locking and Latching-3
This script works on foreign key constraints that have up to eight columns in them (if you have more than that, you probably want to…
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TX (Transaction) Locks- Locking and Latching-3
However, before we can say that we have a good understanding of how the row locking in Oracle works, we must look at one last…