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
a. Create a table odetails_new. It has all the attributes of odetails and an additional column called cost, whose values are the product of the quantity and price of the part bein

Data Types in SQL - Timestamp TIMESTAMP for values representing points in time on a specified uniform scale. DATE is used for timestamps on a scale of one day, such as DATE '2

Project Description: I want to rebuild it and add better content to it It will include up to 5 forms The data will be saved on SQL server and the data access layer could b

Datatype Conversion At times it is necessary to convert a value from one datatype to another. For e.g. if you want to inspect a rowid, you should convert it to a character stri

How Exceptions Are Raised By the run-time system, the internal exceptions are raised implicitly as are user-defined exceptions that you have related with an Oracle error number

I have a Pascal Source file that needs to be compiled into a Service. In addition, there are various functions (Pascal Procedures I guess) that need to be created to Read and Write

Using Cursor Attributes: Every cursor has 4 attributes: %NOTFOUND, %FOUND, %ISOPEN, and %ROWCOUNT. If appended to the cursor name, they return the helpful information about

Using the FORALL Statement The keyword FORALL instruct the PL/SQL engine to bulk-bind input collections before sending them all to the SQL engine. Though the FORALL statement

At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean’s wants to create a trigger that automatically updates the stock level of all pr

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