Transactions handling

Informix®

With the Informix native mode (non ANSI):

Transactions blocks start with BEGIN WORK and terminate with COMMIT WORK or ROLLBACK WORK.
Statements executed outside a transaction are automatically committed.
DDL statements can be executed (and canceled) in transactions.

UPDATE tab1 SET ...   -- auto-committed
BEGIN WORK            -- start of TX block
UPDATE tab1 SET ...
UPDATE tab2 SET ...
...
COMMIT WORK           -- end of TX block

Informix version 11.50 introduces savepoints:

SAVEPOINT name [UNIQUE]
ROLLBACK [WORK] TO SAVEPOINT [name] ]
RELEASE SAVEPOINT name

ORACLE

With ORACLE transactions:

Beginnings of transactions are implicit.
A transaction ends with a COMMIT or ROLLBACK statement.
The current transaction is automatically committed when a DDL statement is executed.

UPDATE tab1 SET ...   -- start of TX block
UPDATE tab2 SET ...
...
COMMIT                -- end of TX block

ORACLE supports savepoints too. However, there are differences:

Savepoints cannot be declared as UNIQUE
Rollback must always specify the savepoint name
You cannot release savepoints (RELEASE SAVEPOINT)

Solution

Regarding transaction control instructions, BDL applications do not have to be modified in order to work with ORACLE. The Informix behavior is simulated with an autocommit mode in the ORACLE interface. A switch to the explicit commit mode is done when a BEGIN WORK is performed by the BDL program.

When executing a DDL statement inside a transaction, ORACLE automatically commits the transaction. Therefore, you must extract the DDL statements from transaction blocks.

If you want to use savepoints, do not use the UNIQUE keyword in the savepoint declaration, always specify the savepoint name in ROLLBACK TO SAVEPOINT, and do not drop savepoints with RELEASE SAVEPOINT.