HP 3000 Manuals HP 3000 Manuals
MPE/iX System Guidelines
On the MPE/iX operating system, the use of the C Queue and the D Queue
can affect performance. The C queue is used primarily for interactive
processes, while the D and E queues are used primarily for batch
operations. You should plan the use of these queues according to the
priorities of the jobs and sessions you run on a regular basis. Monitor
these queues to determine the usage of CPU time. Refer to the
documentation on the MPE/iX TUNE command for more information on
adjusting queues.
Since mapped files are used for the ALLBASE/SQL buffer pool in MPE/iX,
these can also be a source of contention. A large number of separate
DBEnvironments running at the same time can aggravate this situation. A
large number of nondatabase users can also increase contention for
memory.
Using Pseudomapped DBEFiles in MPE/iX
Using pseudomapped files in MPE/iX bypasses the operating system's normal
buffering process. If your users typically use random data access, you
may find that performance improves substantially when you use
pseudomapped DBEFiles. However, if you frequently use sequential access,
you may find that performance drops, since the file system's prefetching
is bypassed.
To create pseudomapped DBEFiles in MPE/iX, create the DBEFiles as usual,
and then use the SQLUtil MOVEFILE command to set the access mode to
pseudomapped. You cannot create pseudomapped log files in MPE/iX.
For information about pseudomapped files, refer to the appendix "Using
Pseudomapped DBEFiles" in the ALLBASE/SQL Database Administration Guide.
Using Memory-Resident Data Buffers
On MPE/iX systems, you can freeze data buffer pages in memory so that
they are not swapped out by the operating system. When you enable this
feature, the operating system does not swap ALLBASE/SQL data buffer pages
in and out of memory.
You should enable memory-resident data buffers if
* the system is used primarily for ALLBASE/SQL database access
* the number of data pages configured for the DBEnvironment is a
small percentage of the overall system memory configuration
To turn on the feature, use the SQLUtil ALTDBE command to set the
MemoryResidentEnabled parameter to YES.
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