/sys$common/syshlp/helplib.hlb Sys Parameters, LNMPHASHTBL  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    LNMPHASHTBL sets the size of the process logical name hash table.
    Logical names are hashed using a function of the name length
    and contents. The LNMPHASHTBL parameter determines the number
    of entries for process-private logical names. The recommended
    setting is the average number of process-private logical names.
    Note that the hashed values are rounded up to the nearest power
    of 2.

    LNMPHASHTBL has the GEN attribute. On VAX systems, LNMPHASHTBL is
    also an AUTOGEN-altered parameter.