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 non-database users can also increase contention for memory. Using Pseudo-Mapped DBEFiles in MPE/iX Using pseudo-mapped files in MPE/iX bypasses the operating system's normal buffering process. Considerable performance benefits can be derived from using pseudo-mapped DBEFiles when the primary data access method is random. However, there may be a performance penalty for sequential access, since the file system's prefetching is bypassed. To use pseudo-mapped DBEFiles in MPE/iX, create the DBEFiles in the normal way, and then use the SQLUtil MOVEFILE command to set the access mode to pseudo-mapped. You cannot create pseudo-mapped log files in MPE/iX. For information about pseudo-mapped files, refer to the appendix "Using Pseudo-Mapped DBEFiles" in the MPE/iX version of 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 this feature is enabled, the operating system does not swap ALLBASE/SQL data buffer pages in and out of memory. Memory resident data buffers should be enabled when the system is used primarily for ALLBASE/SQL database access and 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.