What is Database Commit and Database Rollback.

Question

What is Database Commit and Database Rollback.

Answer 1

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In database level this will be used..
Commit is nothing but SAVE the current record..
If u rol back before commit means whatever u proceeded for the SAVING will be roll back and the data will not be stored..
This will be used,When some times u r filling a register form..after filling 20 fields,In the 21st field u will not to registrer means it will be rollbacked using the Rollbeck command.
In detail--->
ROLLBACK->
In a ROLLBACK, all the changes made by a transaction or a subtransaction on the database instance are reversed.
· Changes closed with a COMMIT can no longer be reversed with a ROLLBACK.
· As a result of a ROLLBACK, a new transaction is implicitly opened.
In normal database operation, the database system performs the required ROLLBACK actions independently. However, ROLLBACK can also be explicitly requested using appropriate SQL statements.
In a restart, the system checks which transactions were canceled or closed with a ROLLBACK. The actions are these transactions are undone.
COMMIT->
In a COMMIT, all the changes made by a transaction or a subtransaction on the database instance are recorded.
· Changes closed with a COMMIT can no longer be reversed with a ROLLBACK.
· As a result of a COMMIT, a new transaction is implicitly opened.
In normal database operation, the database system performs the required COMMIT actions independently. However, COMMIT can also be explicitly requested using appropriate SQL statements.
In a restart, the system checks which transactions were closed with a COMMIT. These actions are redone. Transactions not yet closed with a COMMIT are undone.
From the point of view of database programming, a database LUW is an inseparable sequence of database operations that ends with a database commit. The database LUW is either fully executed by the database system or not at all. Once a database LUW has been successfully executed, the database will be in a consistent state. If an error occurs within a database LUW, all of the database changes since the beginning of the database LUW are reversed. This leaves the database in the state it was in before the transaction started.
the statements
COMMIT WORK.
and
ROLLBACK WORK.
for confirming or undoing database updates. COMMIT WORK always concludes a database LUW and starts a new one. ROLLBACK WORK always undoes all changes back to the start of the database LUW.