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PFCDEFAULT is a system parameter that controls the number of image pagelets read from disk per I/O operation when a page fault occurs. It is available on Alpha and Integrity servers only. The PFCDEFAULT maximum default value is 2032 512-byte pagelets (127 8192-byte Alpha and Integrity server pages). The read I/O operations can take place from an image file or from the page file. The actual size of the cluster can be less than PFCDEFAULT, depending on the size of image sections and the pattern of page references. The value should not be greater than one-fourth the default size of the average working set to prevent a single page fault from displacing a major portion of a working set. Too large a value for PFCDEFAULT can hurt system performance. PFCDEFAULT can be overridden on an image-by-image basis with the CLUSTER option of the OpenVMS linker. PFCDEFAULT has the AUTOGEN and DYNAMIC attributes.