VCC_READAHEAD

   (Alpha and Integrity servers) The dynamic system parameter VCC_
   READAHEAD 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.