Processing transactions, PL-SQL Programming

Processing Transactions

This part describes how to do the transaction processing. You learn the fundamental techniques that safeguard the consistency of your database, involving how to control whether changes to the Oracle data are made permanent or undo.

The jobs or tasks that Oracle manages are termed as the sessions. The user session is started whenever you run an application program or an Oracle tool and connect to the Oracle. To permit the user sessions to work "concurrently" and share the computer resources, the Oracle should control the concurrency, the accessing of similar data by various users. Without sufficient concurrency controls, there might be a loss of the data integrity. That is, the changes to data might be prepared in the wrong order.

Oracle uses the locks to control the concurrent access to data. The lock gives you the temporary ownership of a database resource like a table or a row of data. And hence, the data cannot be changed by other users unless you finish with it. You never require explicitly lock a resource as default locking mechanisms protect the Oracle data and structures. Though, you can request data locks on the tables or rows when it is to your benefit to override the default locking. You can prefer from various modes of locking like the exclusive and row share.

The deadlock can occur when two or many users try to access the similar schema object. For illustration, the two users updating the similar table might wait if each tries to update a row presently locked by the other. As each user is waiting for the resources held by the other user, neither can continue till the Oracle breaks the deadlock by signaling an error to the last participating transaction.

If a table is being queried by one user and updated by the other at similar time, the Oracle generates a read-consistent view of the data for the query. That is, the data read by the query does not change, once a query begins and as it proceeds. The Oracle take snapshot of the table's data and records changes in the rollback segment. The Oracle uses rollback segments to build read-consistent query results and to undo the changes when necessary.

Posted Date: 10/4/2012 4:50:28 AM | Location : United States







Related Discussions:- Processing transactions, Assignment Help, Ask Question on Processing transactions, Get Answer, Expert's Help, Processing transactions Discussions

Write discussion on Processing transactions
Your posts are moderated
Related Questions
Oracle 11 G new features associated with this release:- Enhanced ILM  - Information Lifecycle Management (ILM) has been around for the almost 10 years, but Oracle has made

Need Windows and Linux system Administrator We are seeking a part time system administrator to take care of our servers. Your things to do would add, but not limited to: -

Keyword & Parameter Description: PRAGMA: These keywords signify that the statement is a pragma (i.e. compiler directive). The Pragmas are processed at the compile time, n

Variable Declaration - SQL SQL's support for variables is very similar to Tutorial D's, except that the syntax for creating persistent  variables-base tables-is quite differen

Manipulating Individual Elements Faraway you have manipulated an entire collection. Within the SQL, to manipulate the individual elements of the collection, and then use the ope

Challenge 1 You are required to do the project and write a test plan for it. Demo 4 is a check writer program for employees. In it, the user enters all information about the

I want someone to write a TSQL function that returns the name of the ODBC DSN. I will use the queries below, to get information about the connection, but none of these return th

Data Abstraction The Data abstraction extracts the important properties of data while ignoring the not necessary details. Once you design a data structure, you can fail to reme

How Transactions Guard Your Database The transaction is a sequence of SQL data manipulation statements which does a logical unit of work. The Oracle treats the sequence of SQL

DELETE Command - SQL Loosely speaking, DELETE removes some existing rows from its target table. Suppose the university decides that course C3 is to be withdrawn. Example shows