Connecting distributed database systems

You can use the distributed data facility (DDF) of Db2 to access data that is held by other data management systems. You can also use DDF to make your Db2 data accessible to other systems.

After you install Db2, you can install support for a communications network.

If you plan to use the distributed data facility (DDF), become familiar with the DDF function and the kind of network communications that you want to use to communicate with this Db2 subsystem.

Depending on the network communications that you use, you must install z/OS® UNIX System Services TCP/IP support, Virtual Telecommunications Access Method (VTAM®), or both.

Tip: TCP/IP is the recommended communication protocol for communication with Db2. Although SNA communication remains supported in Db2 13, SNA communication (including the VTAM interface) is deprecated, and support might be removed in the future. You can disable SNA communication by setting the value of the DB2 TCP/IP IPNAME setting. See DB2 TCP/IP IPNAME field.

In Db2 13, you can set up DDF not to activate SNA/APPC support. Therefore, in Db2 13, DDF does not require VTAM to be installed. However, you might need to install VTAM for other reasons.

Communications protocols for DDF

DDF uses TCP/IP or SNA to communicate with other systems.

The following figure shows the connectivity options that you have with DDF in Db2.
Begin figure summary.A figure shows DB2 connecting to other systems.Detailed description available.

Role of the communications database (CDB)

When sending a request, Db2 uses the LINKNAME column of the SYSIBM.LOCATIONS catalog table of the communications database (CDB) to determine which protocol to use.

To receive TCP/IP requests, you must select a DRDA port and a resynchronization port on installation panel DSNTIP5. TCP/IP uses the server's port number to pass network requests to the correct Db2 subsystem.

Figure 1. The LINKNAME column of SYSIBM.LOCATIONS determines protocol
Begin figure summary. A figure shows four boxes that represent four catalog tables. Detailed description available.

To receive VTAM requests, you must specify an LUNAME on installation panel DSNTIPR.

If the value in the LINKNAME column is found in the SYSIBM.IPNAMES table, TCP/IP is used for DRDA connections. If the value is found in SYSIBM.LUNAMES table, SNA is used. If the same name is in both SYSIBM.LUNAMES and SYSIBM.IPNAMES, TCP/IP communication is used.

Attention: A requester cannot connect to a given location using both SNA and TCP/IP protocols. For example, if your SYSIBM.LOCATIONS table specifies a LINKNAME of LU1, and LU1 is defined in both the SYSIBM.IPNAMES and SYSIBM.LUNAMES table, TCP/IP is the only protocol used to connect to LU1 from this requester for DRDA connections.

DDF installation options

The installation options for DDF are described on these installation panels:

Use these options to define, among other things:

  • Whether you want DDF to start automatically when Db2 starts
  • Important names for this Db2 subsystem, including the IPNAME and the LOCATION name, which must be the same for all data sharing members.

    If you plan to use SNA communication with VTAM, you must define an LU name and NETID. Db2 as a requester generates the unit of work using NETID and LUNAME.

  • Thread management options
  • Security options
  • TCP/IP port numbers
  • Control of the number of DRDA query blocks that can flow on a network request that was specified with OPTIMIZED FOR n ROWS where n exceeds the number of rows that fit in a single query block.

If you do not plan on using SNA/APPC communications, you can set up DDF to not activate its SNA/APPC support. To set up DDF to not activate its SNA/APPC support, give the Db2 subsystem an IPNAME value by updating the BSDS DDF record. Setting up DDF to not activate its SNA/APPC support is not supported by the Db2 installation option panels. Db2 TCP/IP communications uses the IPNAME value and a character representation of the TCP/IP resync port (RESPORT) hexadecimal value to identify units of work.

Testing the connections

You should test systems with each other to ensure that their communications setups are correct. If you are testing with another Db2 for z/OS, enter the location name of that other site in field REMOTE LOCATION of installation panel DSNTIPY. The remote location must also have DDF installed and active and must have run the first sample job, DSNTEJ1.