The DB2® Sort default
installation options include options for dynamic sort work allocation,
optimization mode, sensitivity to paging activity, and tuning messages.
Dynamic sort work allocation options
The
following options refer to values used for the dynamic allocation
of sort work data sets. These data sets are de-allocated when the
sort process has completed.
- Sort work DASD pool
- This value specifies the 1- to 8-character name of the group of
devices from which DB2 Sort dynamically
allocates the sort work data sets if SMS is not installed or active
for temporary DASD work data sets. If SMS is active, you can specify
a value for the sort work storage class option. The default value
is SYSDA.
Restriction: You cannot specify VIO as a unit
device.
Note: This value can be overridden at run time.
- Sort work DASD type
- This value specifies the type of DASD with the smallest track
capacity that might be encountered at your installation by a dynamically
allocated sort work data set. If, during dynamic allocation, DB2 Sort receives
a device with a track capacity that is smaller than the one specified,
it might ignore the specified device type. The default value is 3390.
The
following table lists common DASD types and their track capacities:
Table 1. DASD types and their track capacities| DASD type |
DASD track capacity |
|---|
| 3380 |
47476 |
| 3390 |
56664 |
| 9345 |
46456 |
- Number of allocation retry attempts
- This value specifies the number of times that DB2 Sort automatically
retries a dynamic allocation request in situations where sufficient
disk space is not immediately available to satisfy that request. Insufficient
disk space can result in a Sort Capacity Exceeded condition. The minimum
value allowed is 0 and the maximum value is 16. The default value
is 5.
- Minutes between retry attempts
- This value specifies the number of minutes to wait between dynamic
allocation retry attempts. The minimum value allowed is 0 and the
maximum value is 15. The default value is 3.
- Sort work storage class
- This value specifies the storage class that DB2 Sort uses to
manage temporary work data sets for the dynamic allocation of sort
work data sets if SMS is active. If this value is not specified in
an SMS environment, DB2 Sort dynamically
allocates devices from the generic class name that is specified for
the sort work DASD pool. There is no default value for storage class.
Note: An
installation-written automatic class selection (ACS) routine can override
the value you specify.
- Maximum number of sort works
- This value specifies the maximum number of sort work data sets
that can be used. DB2 Sort can
dynamically allocate data sets to bring the total number of sort work
data sets up to the number that you specify. Specify a value from
32 through 255. DB2 Sort automatically
determines the appropriate number of sort work files to use. The default
value is 32.
Note: This value can be overridden at run time.
Optimization mode option
This value specifies
the optimization mode for DB2 Sort.
OPTMODE
- BALANCE
- BALANCE provides the best mix of CPU and
elapsed time performance by balancing utilization of central storage
and disk space. Typically BALANCE uses less
CPU time and more elapsed time than ELAP.
- CPU
- CPU optimizes to minimize CPU time without
any consideration for elapsed time, maximizing disk space usage.
- ELAP
- ELAP optimizes to minimize elapsed time
while significantly reducing CPU time, favoring central storage over
disk space usage. The default value is ELAP.
Note 1: All of these
options limit central storage use if auxiliary storage availability
is low.
Note 2: The OPTMODE value
can be overridden at run time.
Sensitivity to paging activity option
This value specifies the type of storage allocations that DB2 Sort chooses.
PAGEMON
- ON
- Choose
ON only if your system is highly sensitive to
paging activity.
- OFF
- Choose OFF if you use
the defaults for DFSORT's DSPSIZE, HIPRMAX and MOSIZE installation
options. The default value is OFF.
Note: Elapsed time may increase if PAGEMON
is set to ON.
Tuning messages option
This value specifies
whether DB2 Sort displays
additional informational messages for tuning purposes. These tuning
messages provide information about the product's resource utilization,
such as memory usage, sort work DASD space, and sort work EXCPs.
TUNEMSG - ON
- Enables the generation of the additional tuning messages. The
default value is ON.
- OFF
- Suppresses the additional tuning messages.
Note: The TUNEMSG value can
be overridden at run time.