You can define a log stream as either a coupling facility log stream or DASD-only log stream using the DASDONLY parameter on the IXGINVNT REQUEST=DEFINE TYPE=LOGSTREAM service (see The log stream).
Specify or default to DASDONLY=NO, to define a coupling facility log stream. You must also specify a structure name on the STRUCTNAME parameter in the log stream definition for a coupling facility log stream.
Specify DASDONLY=YES, to define a DASD-only log stream, which is not associated with a coupling facility structure. When you define a DASD-only log stream, you can also specify MAXBUFSIZE to define the maximum buffer size that can be written to the DASD-only log stream. (For a coupling facility log stream, MAXBUFSIZE is specified on the IXGINVNT REQUEST=DEFINE TYPE=STRUCTURE request to define the maximum log block size that can be written to the log stream.)
Note that a DASD-only log stream is single-system in scope - only one system may write to a DASD-only log stream.
For set up steps for a DASD-only log stream, see the system logger chapter in z/OS MVS Setting Up a Sysplex.