HP 3000 Manuals HP 3000 Manuals
Processing Time Optimization
The following guidelines can help you improve the efficiency of your
Transact p-code at run-time:
* Adjust the WORK= option of the SYSTEM statement to minimize the
work space recoveries during execution. The number of work space
recoveries can be determined by running test mode 101 or 102.
Adjusting work space size may increase data stack requirements.
* Use DEFINE(INTRINSIC) to call system intrinsics whenever possible.
This construct prevents the Transact processor from using LOADPROC
dynamically to return the P-label of the intrinsic being called.
Using DEFINE(INTRINSIC) reduces the overhead of loading the
Transact program.
* Avoid calling many separate user-defined procedures from a
Transact application. One LOADPROC is executed per procedure,
contributing to processing overhead. If possible, combine all
user-defined procedures into one procedure and identify the
procedure to be executed with a control or index parameter.
* Avoid using the UNLOAD option of the PROC verb with frequently
called procedures, since both LOADPROC and UNLOADPROC are called
each time a procedure is called.
* Use the NOLOAD option of the PROC verb for infrequently called
procedures such as error routines.
* Use UNLOAD to release table entries as appropriate, since the
255-entry/process limit of the Loader Segment Table (LST) is
likely to be exceeded. A preferred approach is to combine
user-defined procedures whenever possible.
* Avoid mixing character modes and block modes during a single
application. This mixture requires considerable overhead in VPLUS
whenever the switch from block mode to character mode occurs.
* Minimize the processing overhead required for opening and closing
forms files by using only one forms file in any program or
subprogram. Only one VPLUS forms file can be opened at a time.
* Avoid switching between segments to minimize the input/output
overhead incurred in loading segment information into the data
stack.
Segments should conform as much as possible to the functional
characteristics of the application. Commonly used routines should
be grouped in the root segment (segment 0), since this segment is
always memory-resident. However, this segment should be as small
as possible.
* Minimize the number of calculations performed. If you need
extensive numeric calculations, consider using subroutines in
other languages and invoking them with the PROC statement.
* Use the MOVE verb whenever possible to transfer values between
data items. The MOVE statement does no data type checks or
conversions. The LET verb, however, performs time-consuming data
type compatibility checks.
* Place frequently referenced data items on the top of the list
register to minimize searches. For example, place them towards
the end of the LIST verb statement. The list register is
implemented as a linked list with list searches starting from the
top of the list.
* Avoid using fragmented lists when accessing databases. Transact
has to unscramble the list before database input/output operations
are performed.
* Minimize internal sorting of large files.
* Follow these guidelines when using the LET verb:
* It is most efficient to use single word integer types (I or
J) for single +, -, =, or negation operations.
* Use long reals (E or R) for single operations that include
*, /, //, LN, LOG, SQRT, or exponentiation, as well as +,
-, =, or negation operations.
* Use packed decimal types (P) for all other operations.
* Avoid mixing types within an operation.
* List the data sets in ascending data set order when using the LOCK
option on the LOGTRAN verb.