What Is a Data Lock

Q

What Is a Data Lock? - Oracle DBA FAQ - Understanding SQL Transaction Management

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A

A data lock is logical flag the Oracle server is placed on data objects to give an exclusive right to a transaction. Statements in other transactions needs to respect data locks based on certain rules. Rules on data locks are:

SELECT query statements do not create any data locks.
INSERT, UPDATE, and DELETE statements create data locks on the affected rows.
Data locks are released when the owner transaction ends.

2007-04-17, 4578👍, 0💬

How To View Existing Locks on the Database
How To View Existing Locks on the Database? - Oracle DBA FAQ - Understanding SQL Transaction Management As can see from the pervious tutorial exercise, performance of the second session is greatly affected by the data lock created on the database. To maintain a good performance level for all session... 2007-04-17, 5904👍, 0💬

What Are Transaction Isolation Levels Supported by Oracle
What Are Transaction Isolation Levels Supported by Oracle? - Oracle DBA FAQ - Understanding SQL Transaction Management Oracle supports two transaction isolation levels: READ COMMITTED (the default option). If the transaction contains DML that requires row locks held by another transaction, then the ... 2007-04-17, 5813👍, 0💬

What Are the General Rules on Data Consistency
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What Are the Restrictions in a READ ONLY Transaction
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How To Set a Transaction To Be READ ONLY
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What Is a Dead Lock
What Is a Dead Lock? - Oracle DBA FAQ - Understanding SQL Transaction Management A dead lock is phenomenon happens between two transactions with each of them holding a lock that blocks the other transaction as shown in the following diagram: (transaction 1) (transaction 2) update row X to create loc... 2007-04-17, 4727👍, 0💬

What Is a Data Lock
What Is a Data Lock? - Oracle DBA FAQ - Understanding SQL Transaction Management A data lock is logical flag the Oracle server is placed on data objects to give an exclusive right to a transaction. Statements in other transactions needs to respect data locks based on certain rules. Rules on data loc... 2007-04-17, 4579👍, 0💬

How Data Locks Are Respected
How Data Locks Are Respected? - Oracle DBA FAQ - Understanding SQL Transaction Management Here are the rules on how data locks are respected: All statements ignore data locks owned its own transaction. SELECT query statements ignores data locks owned by any transactions. INSERT, UPDATE, and DELETE s... 2007-04-17, 4577👍, 0💬

How To Experiment a Data Lock
How To Experiment a Data Lock? - Oracle DBA FAQ - Understanding SQL Transaction Management If you want to have some experience with data locks, you can create two windows runing two SQL*Plus sessions. In session 1, you can run a UPDATE statements to create a data lock. Before committing session 2, s... 2007-04-17, 4557👍, 0💬

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