Rollback Method

Applies To

OSession

Description

This method rolls back the current transaction.

Usage

oresult Rollback(oboolean startnew = FALSE)

Arguments

startnew

If TRUE a new transaction is begun (as if BeginTransaction had been called). If FALSE, no additional work is done after the transaction is committed.

Remarks

A database transaction is a way to group database operations so that they all either succeed or fail together. Please see "Transactions" for more details. BeginTransaction starts a transaction. You can terminate the transaction either with a Commit or a Rollback. It is an error to call Rollback when no transaction is in progress.

Calling Rollback results in OADVISE_ROLLBACK messages being sent to all advisories attached to all dynasets within this session. Any OBinder or OBound objects within the session will have PreRollback and PostRollback triggers called.

Return Value

An oresult indicating whether the operation succeeded (OSUCCESS) or not (OFAILURE).

Example

This example starts a transaction and begins a long sequence of operations. If an error occurs along the way, all changes are discarded with a Rollback. If they all succeed, the changes are made permanent with a Commit.

// routine to give all employees the same salary

void Transfer(ODynaset empdyn, double newsal)

{

// get the session of this dynaset

OSession empsess = empdyn.GetSession();

// start a transaction

empsess.BeginTransaction();

// edit every record (with StartEdit, SetFieldValue, Update)

empdyn.MoveFirst();

while (!empdyn.IsEOF())

{

if (empdyn.StartEdit() != OSUCCESS)

break;

if (empdyn.SetFieldValue("sal", newsal) != OSUCCESS)

break;

if (empdyn.Update() != OSUCCESS)

break;

empdyn.MoveNext(); // go to the next record

}

if (!empdyn.IsEOF())

{ // we got out of the loop early. Get rid of

// any changes we made

empsess.Rollback();

}

else

{ // everything worked. Make it all permanent

empsess.Commit();

}

return;

}