What Are the General Rules on Data Consistency

Home > Oracle > Transaction

Q

What Are the General Rules on Data Consistency? - Oracle DBA FAQ - Understanding SQL Transaction Management

✍: FYIcenter.com

A

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 transactions, the snapshot is taken when the transaction starts.
The snapshot never include uncommitted changes from other transactions.
The snapshot always include uncommitted changes from its own transaction.

2007-04-17, 5409👍, 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, 6449👍, 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, 5410👍, 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, 5410👍, 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, 5389👍, 0💬

How Does Oracle Handle Read Consistency
How Does Oracle Handle Read Consistency? - Oracle DBA FAQ - Understanding SQL Transaction Management Oracle supports two options for you on how to maintain read consistency: READ WRITE (the default option), also called statement-level read consistency. READ ONLY, also called transaction-level read c... 2007-04-18, 5271👍, 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, 5243👍, 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, 5237👍, 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, 5134👍, 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, 5112👍, 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.