During this state, the access to the file is a read, or a write, or (if you like) a series of these actions that you specify. For random mode, a normally distributed seek value is used to move the file pointer before the first record is accessed. For sequential mode, the record number from the last FILE ACCESS phase is used. In this case the file system is told of the sequential access at open time so the read-ahead by the cache manager is maximized.
You can also specify access as using BUFFERED, UNBUFFERED, or MAPPED. Buffered access operations use the file system cache. Unbuffered access operations do not use the cache. Mapped access does not use the file system at all, but instead accesses the file as an array of records in memory. See Chapter 6, "Detecting Cache Bottlenecks," for more information.
After the file is accessed, Response Probe generates the milliseconds of processor time to compute based on the mean and standard deviation supplied.