6. DATA SOURCES › 6.1 SMF Data › 6.1.1 What Is SMF Data?

6.1.1 What Is SMF Data?

IBM's System Management Facilities (SMF) is an integral part
of the z/OS operating system. Its primary function in the
operating system is to collect and record information about
the activities, events, and resource utilizations that occur
throughout the I/S facility.  SMF writes this information, as
SMF data records, in system data sets.  SMF also performs a
secondary function in that it provides macros that can be
used to write customer-developed or vendor product records to
the SMF data sets.

SMF data is the collection of records written to the SMF data
sets by the System Management Facilities or by an external
system using SMF write macros.  The data is written to the
SYS1.MANx data sets (where x can be the letters A-Z and the
numbers 0-9).  These data sets act as a temporary repository
for the data and they are periodically (usually daily)
unloaded to permanent SMF data sets (usually on tape).

SMF records are identified by a number from 0 to 255, which
is referred to as the SMF record type.  Record types 0
through 127 (standard records) are reserved for use by IBM.
Record types 128 through 255 (non-standard records) are set
aside for vendor products and user routines to create their
own SMF records.  SMF provides two macros that are used to
write standard or non-standard records to the SYS1.MANx data
sets.  Non-standard SMF records are typically generated by
vendor products such as CA TSO/MON PM or CA ACF2.  Much in
the same way that z/OS uses SMF to track and record
systemwide resource consumption and activities, these
vendor-generated SMF records show the resource consumption
and activities of the users of their product in more detail
than is available from the z/OS standard record types 0-127.

Some record types, such as the SMF type 30 Common Address
Space Work Record, have record subtypes that dictate how the
contents of the various record fields should be interpreted.
Certain SMF records are fixed length, while others are
variable.

SMF records are written to the SYS1.MANx data sets in
response to certain events.  For example, the IPL of the
system, the end of a TSO session, or the closing of a data
set all constitute events that can trigger the writing of a
standard SMF record.  Interval records are also written in
response to an event -- the expiration of a timer.

The writing of an SMF record to the SYS1.MANx data sets is
usually the culmination of a process that started sometime
earlier.  For example, the writing of a type 30 subtype 4
(step end) record occurs after a series of events that began
with the initiation of the job step.  When the step was first
initiated, control blocks within the step's address space
were set to zeros and blanks.  As the step performed I/Os,
used TCB and SRB time, etc., counts of each utilization were
added to the appropriate control blocks.  As events occurred
within the step, time stamps were created and stored.
Finally, at step end, SMF gathered all the relevant control
block values and formatted them into a type 30 subtype 4
record.  The formatted record was then written to the
SYS1.MANx data set.