generally user exits are used for add the additional
functionality to the sap standard code. it will not effect
to future software upgradation.

but how commit and rollback is used in user exits.

 Hi

I think that we should not write COMMIT in user exit but we can 
write ROLLBACK. Correct me if i am wrong. 

Hi,

Coomit and Roll back in the User exit should not be used.
Because while executing userexit its not allways sure that 
all needed values for database updations are present or 
not.hence we should not use COMMIT or ROLLBACK, of work.
Also userexit is expected to add new functionality to 
existing functionality, its not supposed to make any 
changes in the existing functionality.

Suppose if you take Userexit SAVE_DOCUMENT_PREPARE.Systems 
goes through the user exit more than once and COMMIT or 
ROLLBACK may cause inconsistencies.

Hi,

ofcourse we can write but it is not recommended.

In an user exit control is in the mid of a transaction data 
will be updated or not is decided at the end of the 
execution of the transaction.

If we write Commit it will commit the database update 
whereas case may be like transaction went into error and 
database update is not required in that case there will be 
data inconsistancy.