Concurrency Issue

[Sherjeel]

My desktop appliction is being user by 900+ users concurrently. sometimes what happens is that one user updates a record and is able to view the updated record. the other users are unable to see the changes unless the user (who made the change) logs off. also, the records he made changes to are locked for other users (hence they cant make any changes to those records).
any ideas what may be causing the problem? the application is a simple one as it just updates the database and there arent big transactions, simple one record update

[robertbalmer]

If I understand your problem correctly.

Commit after transaction update in your application... not at time user logs off. Write it in your application code

A table that is being changed is "naturally" locked. This is not a problem but a behaviour.

[dbasan]

sometimes what happens is that one user updates a record and is able to view the updated record. the other users are unable to see the changes unless the user (who made the change) logs off. also, the records he made changes to are locked for other users (hence they cant make any changes to those records).
any ideas what may be causing the problem? the application is a simple one as it just updates the database and there arent big transactions, simple one record update

As Robertbalmer said its Oracle's behavoiur to keep the data consistency.

Once user gives an UPDATE on table it acquires an exclusive lock. change your application code and enforce a COMMIT after an update, which will release the exclusive lock and change to share lock where by other users can see the updated changes immediately after the commit.