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 |
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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 |
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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.
