Named, nested savepoints provide many active savepoints within a transaction.
You can cancel changes between a SAVEPOINT and a RELEASE SAVEPOINT by rolling back to a previous savepoint or rolling back the transaction itself. Changes within a transaction are not a permanent part of the database until the transaction is committed. All savepoints are released when a transaction ends.
Savepoints cause SAP Sybase IQ to update information it maintains about the location of available disk space. This information is used during transaction rollback.
There is no additional overhead in using savepoints, although unreleased savepoints may consume extra disk space by keeping older intermediate versions active.