This requirement applies to coupling facility log streams only. See Determine the right kind of log stream for each application for determining whether you should use coupling facility versus DASD-only log streams.

If you are testing coupling facility function using the Integrated Coupling Migration Facility (ICMF), then system logger requires that ICMF be at coupling facility control code at the same level as above.

The functional capabilities and storage implications associated with each CFLEVEL may vary, see Understanding the coupling facility level (CFLEVEL) to determine which CFLEVEL would be appropriate for system logger's coupling facility structure use. See LOGR couple data set versioning — new format levels to understand the supported system logger functional capabilities for the different LOGR CDS format levels.