Unlocks all the physical libraries in the current virtual library
    list so that they can be modified.

    Format

      SCA$UNLOCK_LIBRARY  command_context

1  –  Argument

 command_context
    type:       $SCA_COMMAND_CONTEXT
    access:     read/write
    mechanism:  by reference

    An SCA command context.

2  –  Condition Value Returned

    SCA$_NORMAL           The libraries have been successfully
                          unlocked.

3  –  Description

    The SCA$UNLOCK_LIBRARY routine unlocks all the physical libraries
    in the current virtual library list so that they can be modified.