ALLBASE/SQL Reference Manual (36216-90216)

Chapter 2 99

Using ALLBASE/SQL

Using Multiple Connections and Transactions with Timeouts

If DBERR 2825 is returned, the transaction has timed out, and you must take

appropriate action.

Further discussion of timeout functionality is provided in the ALLBASE/SQL Advanced

Application Programming Guide.

Setting the Transaction Mode

The SET MULTITRANSACTION statement allows you to switch between single-transaction

mode and multi-transaction mode.Single-transaction mode implies sequential execution of

transactions across a set of DBEnvironment connections. When your application requires

multiple, simultaneous transactions, you must choose multi-transaction mode.

WARNING

When using multi-transaction mode, be sure the current timeout

value for all connections is set to a value other than NONE (inﬁnity).

This eliminates the possibility of an inﬁnite wait if an undetectable

deadlock or wait condition occurs.

Using Single-Transaction Mode

If your application contains queries for two or more databases and you want to

sequentially execute a single transaction against each database, you can use

single-transaction mode. This mode is the default and is standards compliant. The

following example illustrates the use of single-transaction mode in ISQL:

1. Put single-transaction mode in effect.

isql=> SET MULTITRANSACTION OFF;

2. Connect to two DBEnvironments.

isql=> CONNECT TO 'PartsDBE' AS 'Parts1';

isql=> CONNECT TO 'SalesDBE' AS 'Sales1';

3. Set the current connection to Parts1.

isql=> SET CONNECTION 'Parts1';

4. Begin a transaction for PartsDBE.

isql=> BEGIN WORK RC;

isql=> SELECT PartNumber, PartName, SalesPrice

> FROM PurchDB.Parts

> WHERE PartNumber BETWEEN 20000 AND 21000;