For a coupling facility log stream, system logger requires that a coupling facility list structure be assigned for each log stream as interim storage. When an application writes data to a coupling facility log stream, it is first written to the coupling facility list structure for that log stream. System logger manages connections to the coupling facility, but the installation must define coupling facility structures dedicated to log streams in the LOGR policy as part of the planning process for system logger applications. More than one log stream can share space in a single structure.

System logger will dynamically manage the entry-to-element ratio for log stream coupling facility structures. The installation defines an initial average buffer size for a structure on the AVGBUFSIZE parameter in the LOGR policy using the IXGINVNT service or the IXCMIAPU utility. System logger uses this value to determine the initial entry-to-element ratio for the structure. After that, system logger will dynamically manage the entry-to-element ratio for the structure based on actual structure usage. The most current entry-to-element ratio is used on any subsequent allocations of the structure.