HP 3000 Manuals HP 3000 Manuals
HP-UX System Guidelines
This section presents some pointers about parameters in the HP-UX
operating system that can affect the performance of ALLBASE/SQL.
* Since the Series 300 has no native packed decimal type, DECIMAL
values involved in calculation must be converted to FLOATs and
then back to DECIMAL. This can degrade performance.
* Use the default rotational delay of 4ms. Selecting a different
value can degrade the performance of serial scans. For additional
information, refer to the HP-UX man page for the tunefs command.
* Use an HP-UX buffer cache that is at least as large as the default
cache size (10% of physical memory on the Series 800). Use more
than the default for large tables, or indexed joins.
* For large multi-user operations on Series 800 systems, put swap
space on a spindle different from DBEnvironment files and from the
log files. Increase the size of swap space if you are running
more than 32 users.
* Use a file blocking factor of at least 4K for best results with
DBEFiles. Serial scans may benefit from a blocking factor of 8K
or larger.
* Use a larger interval for the sleep time for hpdbdaemon than the
default of 30 seconds. The daemon is a process that wakes up
every 30 seconds and connects to the DBEnvironment to determine
whether there have been any abnormal terminations. If there have
been abnormal terminations, the daemon cleans up by releasing
locks and other system resources. If your system rarely
experiences abnormal terminations, you can avoid the overhead of
the daemon's connecting to and releasing the DBEnvironment every
thirty seconds by increasing the sleep time. You should
experiment with different intervals; a value of 60 seconds reduces
the overhead by half. Remember, however, that increasing the
sleep time also increases the time before cleanup takes place.
You can set the daemon's sleep time with the C shell setenv
command, as follows:
setenv hpdbdmonsl n
where the integer n is a number of seconds.
* Use the formula described under "Choosing the Number of Data
Buffer Pages" to help determine the maximum number of data buffer
pages to use on series 800 systems, where the maximum is limited
by the size of swap space.
* You can use the HP-UX nice command to adjust the priority of
executing processes. Refer to the man page for nice.
Using HP-UX Raw Files for DBEFiles and Logs
Using raw files in HP-UX bypasses the operating system's normal buffering
process. Considerable performance benefits can be derived from using raw
files for logs and for DBEFiles when the primary data access method is
random. However, there may be a performance penalty for sequential
access to DBEFiles, since the file system's prefetching is bypassed.
In HP-UX, you can create raw DBEFiles and log files by specifying the
pathname of a raw device in the CREATE DBEFILE statement or in LOG
DBEFILE clause of the START DBE NEW and START DBE NEWLOG statements.
For more information about raw files, refer to the appendix "Using HP-UX
Raw Files for DBEFiles and Logs" in the HP-UX version of the ALLBASE/SQL
Database Administration Guide.