VSAM CDC Connector > Introduction to VSAM CDC Connector > VSAM CDC Connector rules and guidelines

VSAM CDC Connector rules and guidelines

Review the VSAM CDC Connector rules and guidelines before you begin configuring connections, mappings, and mapping tasks.

•You can use VSAM CDC connections for sources only. Do not select this connection type for a target.
•You must configure remote logging of VSAM change records to a PowerExchange Logger for Linux, UNIX, and Windows (LUW) instance. For more information, see the PowerExchange CDC Guide for Linux, UNIX, and Windows.
•VSAM CDC Connector connects to the PowerExchange Listener on the PowerExchange Logger for LUW system by using the Listener Location property that you specify in the VSAM CDC connection definition. On the Connector system, you do not need to create a local copy of the DBMOVER configuration file that contains a NODE statement pointing to the PowerExchange Listener.
•If you upgrade your system to a later PowerExchange version, you must stop the Secure Agent that connects to the older PowerExchange Listener before you try to connect to the upgraded PowerExchange Listener. After you edit the connection properties to specify the upgraded PowerExchange Listener, restart the Secure Agent before you try to establish the connection again.
•The PowerExchange Listener on the LUW system can compress or encrypt the change data that it sends to the PWX CDC Reader component of VSAM CDC Connector, depending on how you set the Compression and Encryption properties for the source connection.
•VSAM CDC Connector supports PowerExchange Logger for LUW group definition files. A group definition file creates a separate set of PowerExchange Logger log files for each defined group of registered VSAM source data sets. When a mapping task runs, the PWX CDC Reader reads only the subset of log files for the group that contains the source data set.
•If you include multiple VSAM source data sets in a mapping, the PWX CDC Reader automatically uses group source processing to read change records for all of the data sets in a single pass.
•The PWX CDC Metadata Adapter retrieves information for registered VSAM source data sets from the PowerExchange extraction-map data set, DTLCAMAP, on the CICS/VSAM source system, provided that you specify the Map Location, Map User, and Map Password properties for the source connection. The Adapter retrieves information only from PowerExchange-generated extraction maps that have names beginning with "d." The extraction maps provide information, such as the incoming fields, that will be used when you create a mapping. The Adapter does not retrieve information from user-defined extraction maps that have names beginning with "u" for user-defined.
• The PowerExchange change data extraction modes, as defined in the PowerExchange CDC Guide for Linux, UNIX, and Windows, do not pertain to VSAM CDC Connector. The PWX CDC Reader component of VSAM CDC Connector extracts change records until it reaches the end-of-log in the PowerExchange Logger log files and then stops. However, the PowerExchange configuration that the PWX CDC Reader requires is similar to the configuration for continuous extraction mode in the following ways:

- A CAPX CAPI_CONNECTION statement must exist in the PowerExchange DBMOVER configuration file on the PowerExchange Logger for LUW system.
- The capture registrations for VSAM source data sets must specify Part for the Condense option.

• The maximum network buffer size that the PowerExchange Listener can use for sending data is 8 MB. If you have a mapping with an extremely large VSAM source data set, this maximum buffer size might be exceeded. In this case, the mapping task fails with the following error:

PWXPC_10034 [date time] [ERROR] CDCDispatcher cannot fetch changed data from the PowerExchange Listener. Error code: [271]

•If you change the source object in a mapping that has been used for CDC processing, create a new mapping task for the mapping. If you need to retain the mapping task that is currently associated with the mapping, increment the revision number in the CDC Runtime properties for the mapping task.

•The CICS/VSAM ECCR can capture changes only from local VSAM ESDS, KSDS, RRDS, or VRRDS data sets and CICS-maintained data tables.
•The CICS/VSAM ECCR can capture change data from ESDS data sets that use either the 32-bit relative byte addressing (RBA) and 64-bit extended relative byte addressing (XRBA). The ECCR does not capture change data for the following types of ESDS items:

- Spanned ESDSs
- Paths defined over ESDSs
- An alternate Index (AIX) that points to an ESDS base cluster

For more information, see the "CICS/VSAM Change Data Capture" chapter in the PowerExchange CDC Guide for z/OS.