Home > Software > Data-Warehouse > DataStage
Interview Questions   Tutorials   Discussions   Programs   Discussion   

DataStage - What is isolation level and when do we use them?

asked mar September 20, 2014 06:32 AM  

What is isolation level and when do we use them?


1 Answers

answered By vishnoiprem   0  
Specifies the transaction isolation levels that provide the necessary
consistency and concurrency control between transactions in the job and other transactions for optimal performance.

  • Because Oracle does not prevent other transactions from modifying the data read by a query, that data may be changed by other transactions between two executions of the query. Thus, a transaction that executes a given query twice may experience both nonrepeatable reads and phantoms. Use one of the following transaction isolation levels:
  • Read-only. Sees only those changes that were committed when the transaction began. This level does not permit INSERT, UPDATE, and DELETE statements
  • Read Committed. Takes exclusive locks on modified data and shareable locks on all other data. Each query executed by a transaction sees only data that was committed before the query (not the transaction) began. Oracle queries never read dirty, that is, uncommitted data. This is the default.
  • Serializable. Takes exclusive locks on modified data and sharable locks on all other data. It sees only those changes committed when the transaction began plus those made by the transaction itself through INSERT, UPDATE, and DELETE statements. Serializable transactions do not experience nonrepeatable reads or phantoms.
   add comment

Your answer

Join with account you already have



 Write A Tutorials
Online-Classroom Classes

  1 person following this question

  1 person following this tag

  Question tags

datastage × 4

Asked 2 years and 3 months ago ago
Number of Views -752
Number of Answers -1
Last updated
3 years and 2 months ago ago

Ready to start your tutorial with us? That's great! Send us an email and we will get back to you as soon as possible!