Embedded SQL Programming Guide

Distributed Unit of Work with DB2 Connect

DB2 Connect allows you to update multiple databases within a single distributed unit of work (DUOW). Whether you can use this capability depends on several factors:

Your application program must be precompiled with the CONNECT 2 and SYNCPOINT TWOPHASE options.
Databases which are connected over SNA links (node type APPC) can be updated using two-phase commit (2PC) through DB2 Connect in a single unit of work, as long as:
- The LU 6.2 Syncpoint Manager is installed on AIX or OS/2.
- The right software prerequisites are installed and configured appropriately: IBM SNA Server for AIX Version 3.1 or higher, or IBM Communications Server for OS/2 Version 4 or higher. (For further information refer to the chapter Setting Up Two-phase Commit Using SNA in DB2 Connect Enterprise Edition Quick Beginnings).
- The databases are one of:
  - DB2 for OS/390, Version 5.1 or later
  - DB2 for AS/400, Version 3.1 or later
  - DB2 for MVS/ESA, Version 3.1 or later
  - DB2 for VSE & VM, Version 5.1 or later
  This is regardless of whether CICS or Encina is being used.
  Additionally, the DB2 Connect Enterprise Edition Version 5 Syncpoint Manager continues to allow DB2 MVS Version 3.1 databases to participate in two-phase commit, but not to act as the TM_DATABASE for such transactions.
DB2 for OS/390 Version 5 databases connected over TCP/IP links (node type TCPIP) can also participate in units of work using two-phase commit, and they are also able to participate with DB2 Universal Database Version 5 databases in the same transaction. When using TCP/IP, DB2 for OS/390 can be defined as the TM_DATABASE.

Notes:

DB2 Common Server Version 2.1 databases can be updated with two-phase commit in a unit of work only when DB2 for OS/390 Version 5.1 is not the transaction manager database.
If the TM_DATABASE for the transaction is DB2 for OS/390 Version 5.1, then DB2 CS V2.1 databases participating in that transaction become READ-ONLY for the client application.
Mixed connection scenarios for DB2 Universal Database Version 5 client applications are only supported if DB2 for OS/390 Version 5.1 is the TM_DATABASE for the transaction. For further information refer to the chapter Setting Up Two-phase Commit Using TCP/IP in DB2 Connect Enterprise Edition Quick Beginnings.
The database levels supported for two-phase commit transactions over TCP/IP depend on the Client Application Enabler level, the TM_DATABASE level, and the participant database levels.
We strongly recommend that all clients accessing DB2 Universal Database Version 5 and DB2 for OS/390 Version 5 databases be at DB2 Universal Database Version 5 level. DB2 Version 2.1 clients cannot initiate two-phase commit transactions if DB2 for OS/390 Version 5 databases participate in the transaction.

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