Self-defining sections

A self-defining section of a type 115 SMF record tells you where to find a statistics record, how long it is, and how many times that type of record is repeated (with different values). The self-defining sections follow after the header, at fixed offsets from the start of the SMF record. Each statistics record can be identified by an eye-catcher string.

Eight types of self-defining section are available to users for type 115 records. Each self-defining section points to statistics data related to one of the WebSphere MQ components. Table 16 summarizes the sources of the statistics, the eye-catcher strings, and the offsets of the self-defining sections from the start of the SMF record header.

Table 16. Offsets to self-defining sections Offsets are from the start of the SMF record and are fixed for each type of statistics source.
Source of statistics Record subtype (SM115STF) Offset of self-defining section Length of data Eye-catcher of data
Dec Hex
Storage manager 1 100 X'64' X'48' QSST
Log manager 1 116 X'74' X'78' QJST
Message manager 2 36 X'24' X'30' QMST
Data manager 2 44 X'2C' X'50' QIST
Buffer manager - one for each buffer pool 2 52 X'34' X'68' QPST
Lock manager 2 60 X'3C' X'20' QLST
DB2 manager 2 68 X'44' X'1E0' Q5ST
Coupling Facility manager 2 76 X'4C' X'1008' QEST
Note:
Other self-defining sections refer to data for IBM use only.

Each self-defining section is two fullwords long and has this format:

   ssssssssllllnnnn

where:

ssssssss Fullword containing the offset from the start of the SMF record.
llll Halfword giving the length of this data record.
nnnn Halfword giving the number of data records in this SMF record.

Figure 18 shows an example of part of an SMF type 115 subtype 2 record. The numbers in the left-hand column represent the offset, in hexadecimal, from the start of the record. Each line corresponds to sixteen bytes of data, where each byte is two hexadecimal characters, for example 0C. The characters in the right-hand column represent the printable characters for each byte. Non-printable characters are shown by a period (.) character.

In this example, alternate fields in the SMF header are underlined to help you to see them; refer to Table 15 to identify them. The self-defining sections for the message manager statistics data records (at the offset given in Table 16) and buffer manager statistics are shown in bold.

Figure 18. Part of an SMF record 115 showing the header and self-defining sections

000000  14A00000 5E730035 55750100 223FD4E5  *....;.........MV* 
000010  F4F1D4D8 F0F70002 F6F0F000 0000147C  *41MQ07..600....@* 
000020  00240001 00000054 00300001 00000084  *................* 
000030  00500001 000000D4 00680004 00000274  *.&.....M........* 
000040  00200001 00000294 01E00001 00000474  *................* 
000050  10080001 D40F0030 D8D4E2E3 00000000  *....M...QMST....* 

The self-defining section for message manager statistics is located at offset X'20' from the start of the SMF record and contains this information:

  • The offset of the message manager statistics is located X'00000054' bytes from the start of the SMF record.

  • The message manager record is X'0030' bytes long.

  • There is one record (X'0001').

Similarly, the buffer manager self-defining section at X'30' specifies that the offset to the buffer manager statistics is X'000000D4', is of length X'0068', and occurs X'0004' times.

Note:
Always use offsets in the self-defining sections to locate the statistics records.