VMS Help Sys Parameters, ACP_SWAPFLGS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    ACP_SWAPFLGS enables or disables swap through the value of a
    4-bit number for the following four classes of ACPs:

    Bit    Class of ACP

    0      Disks mounted by MOUNT/SYSTEM
    1      Disks mounted by MOUNT/GROUP
    2      Private disks
    3      Magnetic tape ACP

    If the value of the bit is 1, the corresponding class of ACPs
    can be swapped. The value of decimal 15 (hexadecimal F-all bits
    on) enables swap for all classes of ACP. A value of decimal
    14 disables swap for ACPs for volumes mounted with the /SYSTEM
    qualifier but leaves swap enabled for all other ACPs. Note that
    one has only disk ACPs present if they are specifically requested
    at mount time or if a Files-11 On-Disk Structure Level 1 disk is
    mounted. In general, only bit 3 is significant because usually no
    file ACPs exist.

    ACP_SWAPFLGS is an AUTOGEN and DYNAMIC parameter.