Saving initialization messages in a data set

The IOEFSPRM msg_output_dsn option specifies the name of a data set that contains output messages that come from the zFS PFS during zFS initialization. This option might be helpful for debugging because the data set can be sent to IBM® service if needed. The msg_output_dsn option is optional. If it is not specified, zFS PFS messages go only to the system log. If it is specified, the data set should be preallocated as a sequential data set with a RECFM=VB and LRECL=248 and should be large enough to contain all zFS PFS initialization messages between restarts. The space used depends on how many zFS initialization messages are issued. A suggested primary allocation is two cylinders with a secondary allocation of two cylinders. If the data set fills up, no more messages are written to the data set. (They still go to the system log.) After zFS restarts, the message output data set is overwritten.