Dml by multiple users/commit scenarios in oracle?

Transactions are not seen outside of your session until you commit. If another user logs in, then they will see the table as it was stored in the database at its last committed state. That is the reason for undo space, redo logs, etc.In your scenario, User B would not see A's transaction even though B has committed his, because A has not committed their changes.

For full details of Data Concurrency and Transactions in Oracle see the Oracle Concepts Guide.

Thanks for the link. – ssr532 Jul 8 '10 at 6:13.

It is possible for multiple insert dml operations to collide even though uncommitted. If the insert into emp above is inserting into a uniquely indexed column (e.g. , a primary key), then until committed or rolled back user B cannot insert the same value - it will block.So, in a sense, user B "sees" the uncommitted insert by A, although user B cannot select the values inserted by A.

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