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VCC_READAHEAD is a system parameter that controls whether the extended file cache can use read- ahead caching. Read-ahead caching is a technique that improves the performance of applications that read data sequentially. By default VCC_READAHEAD is 1, which means that the extended file cache can use read-ahead caching. The extended file cache detects when a file is being read sequentially in equal-sized I/Os, and fetches data ahead of the current read, so that the next read instruction can be satisfied from cache. To stop the extended file cache from using read-ahead caching, set VCC_READAHEAD to 0. Changing the value of VCC_READAHEAD affects volumes currently mounted on the local node, as well as volumes mounted in the future. Readahead I/Os are totally asynchronous from user I/Os and only take place if sufficient system resources are available. VCC_READAHEAD is a DYNAMIC parameter. This parameter is available on Alpha and Integrity systems only.