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VCC_MAX_CACHE is a system parameter that controls the maximum size of the extended file cache. It specifies the size in megabytes. By default, VCC_MAX_CACHE has a special value of -1 for people who do not want to tune their systems manually; this value means that at system startup, the maximum size of the extended file cache is set to 50 percent of the physical memory on the system. The extended file cache can automatically shrink and grow, depending on your I/O workload and how much spare memory your system has. As your I/O workload increases, the cache automatically grows, but never to more than the maximum size. When your application needs memory, the cache automatically shrinks. The value of VCC_MAX_CACHE at system startup sets an upper limit for the maximum size of the extended file cache. You cannot increase the maximum size of VCC_MAX_CACHE beyond its value at boot time. For example, if VCC_MAX_CACHE is 60 MB at system startup, you can then set VCC_MAX_CACHE to 40, which decreases the maximum size to 40 MB. If you then set VCC_MAX_CACHE to 80, the maximum size is only increased to 60 MB, the value set at system startup. Note that VCC_MAX_CACHE is a semi-dynamic parameter. If you change its value, you must enter the DCL command SET CACHE/RESET for any changes to take effect immediately. Otherwise, it might take much more time for the changes to take effect. If you are using the reserved memory registry to allocate memory permanently, you must set the VCC$MIN_CACHE_SIZE entry in the reserved memory registry to a value less than or equal to VCC_MAX_CACHE at system startup time. VCC_MAX_CACHE is a DYNAMIC parameter. It is available on Alpha and Integrity servers only.

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