Virtual Lookaside Facility (VLF)

The virtual lookaside facility (VLF) is a set of MVS services that provide a high-performance alternate path method of retrieving named objects from DASD on behalf of many users. VLF is designed primarily to improve the response time for such applications.

VLF uses data spaces to hold data objects in virtual storage as an alternative to repeatedly retrieving the data from DASD.

VLF keeps objects (for example Load modules) in Virtual Storage in order to save I/O operations that would load such objects. Designed primarily to improve performance by retrieving the most currently used objects from Virtual Storage rather then performing repetitive I/O operations from DASD.VLF can be configured by using PARMLIB member COFVLFxx.

Starting VLF

S VLF,SUB=MSTR

Invokes the VLF procedure that starts the virtual lookaside facility (VLF).

NN=xx

Indicates that the system is to start VLF using the COFVLFxx member of the logical parmlib or that the system is to start DLF using the COFDLFxx member of the logical parmlib. In each case, replace xx with two alphanumeric characters that match the suffix of the parmlib member.

Stopping  VLF

P VLF

Parm lib



COFVLFxx



CLASS     NAME(classname)

          {EDSN(dsn1) [VOL(vol)] EDSN(dsn2)...}

          {EMAJ(majname1) EMAJ(majname2)...}

          [MAXVIRT(nnn)]