- DDNAME=
- Specifies the name (1 to 8 characters) of the DD statement that
defines the spool data set. Once a spool data set is defined, it must
be referred to by the same ddname.
- SPART=
- Specifies that the spool data set identified by this statement
is a member of the named spool partition. The partition name must
match a partition name specified on a SPART statement.
To specify
that the data set is a member of the default partition, omit this
parameter. You must assign at least one spool data set as a member
of the default spool partition, or you must allow at least one spool
data set to become a member by default. If you fail to do this, JES3
terminates its processing during initialization.
- STT=
- Specifies the range of cylinders to be allocated to the single
track table (STT). This range must be within the extent allocated
to the data set. The value of cylnum specifies
an absolute cylinder number. (Absolute cylinder numbers are device-dependent;
the component description for the device describes the numbering scheme.)
The
range indicated by (cylnum,cylnum) can
be one cylinder (for example: 24,24) or several cylinders (for example:
24,28) and can be in ascending or descending order. JES3 allocates
to the STT only those track groups that fall completely within the
indicated range of cylinders. The value for cylnum cannot
be 0.
For fixed head devices, allocate cylinders under the
fixed heads for better performance. For other devices, allocate cylinders
in the center of the data set.
You should consider spool recovery
and I/O balance before specifying the STT or STTL parameter. The
presence of a single track table on a spool extent can limit the recovery
actions that can be taken for that spool extent. To ensure successful
recovery in the event of a problem, you should dedicate a spool extent
to the STT or specify the STT on the minimum number of spool extents
to achieve your I/O balance requirements.
If you omit either
the STT or STTL parameter, or you specify an invalid range, JES3 allocates
the centermost 2 track groups of each spool data set in the default
partition as the initial STT allocation.
Note: If you
change this parameter and want the change to go into effect for existing
spool data sets, you must perform a cold start.
- STTL=
- Specifies the location and number of track groups to allocate
to the single track table (STT). These track groups must be within
the extent allocated to the data set. The value for cylnum specifies an absolute cylinder number
indicating the beginning cylinder number of the STT allocation in
this extent. (Absolute cylinder numbers are device-dependent; the
component description for the device describes the numbering scheme.)
The value for numtrkgps specifies the
number of track groups to allocate to this extent, beginning with
the first track group that is located completely in cylinder cylnum. The maximum number of track groups
that may be allocated to the STT is 9999.
For fixed head devices,
allocate cylinders under the fixed heads for better performance. For
other devices, allocate cylinders in the center of the data set.
You
should consider spool recovery and I/O balance before specifying the
STT or STTL parameter. The presence of a single track table on a
spool extent can limit the recovery actions that can be taken for
that spool extent. To ensure successful recovery in the event of
a problem, you should dedicate a spool extent to the STT or specify
the STT on the minimum number of spool extents to achieve your I/O
balance requirements.
If you omit either the STT or STTL parameter,
or you specify an invalid range, JES3 allocates the centermost 2 track
groups of each spool data set in the default partition as the initial
STT allocation.
Note: If you change this parameter and
want the change to go into effect for existing spool data sets, you
must perform a cold start.
z/OS JES3 Initialization and Tuning Reference
Copyright IBM Corporation 1990, 2014