Installations that choose to read the SMF data sets directly rather than using the SMF data set dump program, should note that SMF preformats its data sets with dummy records. A dummy record is shorter than any valid SMF record and is easily identified because it contains the characters “SMFEOFMARK”. The SMF data set dump program terminates processing when it encounters a dummy record, thereby improving data set processing performance.
Cancelling the SMF data set dump program is not advised, as it can leave the SMF data sets in an unpredictable state.
Programs that access the output of the SMF data set dump program are required to specify the correct logical record length (LRECL) value. Failure to specify a large enough LRECL value might result in an 002 abend. The LRECL value must equal the length of the longest SMF record being created plus four bytes for the record descriptor word (RDW). The LRECL value can be larger than the BLKSIZE value because the records can be segmented.
Your installation can give control during dump processing to three 24-bit addressable installation exit routines. By doing this, you can examine or modify the record before it is written. When each exit is invoked, register 1 contains the address of a three-word parameter list (Figure 1).
- word 1
- register 0 on entry to the SMF data set dump program
- word 2
- register 1 on entry to the SMF data set dump program
- word 3
- reserved for user. This word is initialized to zero before the first installation exit is invoked.
The contents of the second and third words depend on the installation exit being invoked. The installation exits are described in Specifying parameters for the SMF data set dump program.