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HP OpenVMS Systemsask the wizard |
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The Question is: Alpha 2100 Openvms 7.1-1h2 3-300mhz cpu's, 3-512 memory boards running oracle 7.3.2.3 I am reviewing the OpenVMS Performance Manual and it recommends that a capacity upgrade be performed because it is a waste of time to manually tweek the system. I will perform all the monitors etc to analyze my system, with the 4th slot open, do I gain more overall performance by adding a 4th CPU or a 4th 512 memory board? Or save the money and buy a 4100 next year and put NT on it. The Answer is : There are many factors involved in system performance tuning. (As you have found, there is an entire manual on this topic...) Manual tuning will typically provide roughly a 10% improvement over what an unencumbered AUTOGEN with FEEDBACK can provide, and manual tuning requires extensive time and effort for data gathering and analysis, as well as for trial and error. Such tweaking is highly dependent on the particular application and OpenVMS version, and retweaking after an upgrade is often required. Without knowing what the particular system performance limitation is, the particular suggested upgrade is not obvious -- suggesting tuning without system access is particularly difficult. Incorrect tuning can dramatically reduce system performance. As a first step, clean the cruft out of MODPARAMS.DAT, and replace any absolute assignments with the appropriate of MIN_, MAX_, and ADD_ when appropriate, and run several passes of AUTOGEN with FEEDBACK over the next couple of weeks (or over a sufficient example of your typical system load). Use this as your tuning baseline. Multiprocessor upgrades can be useful when the system is CPU limited and your application(s) can operate in parallel. Multiprocessor upgrades are not useful when the particular application(s) are single-stream or the system is I/O limited. Memory upgrades can be useful when the system is memory limited, and increased memory availability can reduce I/O loading through enlaged caching. Faster processor upgrades -- not available for the AlphaServer 2100 5/300 series running OpenVMS -- are an alternative when the system is I/O limited (I/O completion is handled by the primary processor). (As a general rule, two processors of speed X are generally less desirable than one processor of speed 2X. As a general rule, each additional processor of speed X added into a multiprocessor system will provide a decreasing performance improvement, and eventually enough processors can be added that no improvement or even a performance reduction will be realized.) Appropriate process working sets and process quotas can significantly contribute to system and application performance. In addition to the older AlphaServer 4100 series, other potential upgrades include the AlphaServer DS20 and AlphaServer ES40 systems. (But if the application is currently limited by the performance of a current-generation SCSI disk, upgrading the processor won't help over-all performance -- the goal is to identify and remove the particular performance-limiting factor.)
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