What Is a Data Lock

Q

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

✍: FYIcenter.com

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, 5306👍, 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, 6775👍, 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, 6527👍, 0💬

How To Set a Transaction To Be READ ONLY
How To Set a Transaction To Be READ ONLY? - Oracle DBA FAQ - Understanding SQL Transaction Management If you want a transaction to be set as READ ONLY, you need to the transaction with the SET TRANSACTION READ ONLY statement. Note that a DML statement will start the transaction automatically. So you... 2007-04-17, 5543👍, 0💬

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, 5539👍, 0💬

What Are the General Rules on Data Consistency
What Are the General Rules on Data Consistency? - Oracle DBA FAQ - Understanding SQL Transaction Management All SQL statements always work with a snapshot of the database to provide data consistency. For READ WRITE transactions, the snapshot is taken when each statement starts. For READ ONLY transac... 2007-04-17, 5491👍, 0💬

What Are the Restrictions in a READ ONLY Transaction
What Are the Restrictions in a READ ONLY Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management There are lots of restrictions in a READ ONLY transaction: You can not switch to READ WRITE mode. You can not run any INSERT, UPDATE, DELETE statements. You can run SELECT query statemen... 2007-04-17, 5473👍, 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, 5316👍, 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, 5307👍, 0💬

What Is a READ ONLY Transaction
What Is a READ ONLY Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management A READ ONLY transaction is a transaction in which the read consistency is set at the transaction level. In a READ ONLY transaction, a logical snapshot of the database is created at the beginning of the trans... 2007-04-17, 5206👍, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.