The PowerExchange Logger prepares to write data to log files when it receives a message from an ECCR. The PowerExchange Logger retrieves logged data when it receives a request from an log reader that specifies a relative byte address (RBA) as the starting point for data transfer.

When you use real-time extraction mode to read change data, the PowerExchange Listener passes a Resource Interest List that contains the EDMNAMEs of the capture registrations in the extraction process to the PowerExchange Logger. The PowerExchange Logger uses this list to filter out change records for EDMNAMEs that are not included in the extraction process, which reduces the resource consumption of the log read process in the PowerExchange Listener.

The IBM Cross-System Coupling Facility (XCF) controls the connection from other components to the PowerExchange Logger. The number of log readers that can request data from the PowerExchange Logger is limited to the maximum number of members that can join an XCF group. The maximum members in an XCF group is z/OS release dependent and controlled through the XCF MAXMEMBER specification used when defining the SYSPLEX Couple data sets.

The following figure shows the PowerExchange Logger data flow and control flow:

You can control the PowerExchange Logger by running batch change utility procedures that perform the following functions:

You can also issue interactive commands to the PowerExchange Logger.