If the goal of minimizing physical memory utilization is to be achieved when running IRAF, it is essential that the IRAF shared library be "installed" in VMS system shared memory. Further memory savings through memory sharing can be achieved if some of the more commonly used IRAF executables are also installed. This becomes increasingly important as the number of IRAF users increases, but some memory savings may result even if there is only one user, since a single user may spawn batch jobs. Hence, the shared library s_iraf.exe should always be installed if IRAF is used at all, and cl.exe and x_system.exe are used by all IRAF jobs and should be installed if there is usually at least one IRAF user on the system. If there are usually several IRAF users on the system x_images.exe and x_plot.exe are probably worth installing as well.
Installation of task images in system shared memory is done with the VMS INSTALL utility, which requires CMKRNL privilege to execute (also discussed in §2.3.2). Installation of the IRAF shared library and other task images is most conveniently done by executing the INSTALL.COM command procedure in hlib. The list of files to be installed is in INSTALL.LST. This file should be reviewed and edited during system installation to select those images to be installed on the local host. Then INSTALL.COM may be directly executed to temporarily install the images, but to permanently install the images the system bootstrap procedure should be modified to execute the INSTALL.COM script (or explicitly install the images by name) whenever the system is booted. Note that the global pages used by an installed image are not actually freed until any and all processes using those global pages terminate.
The procedure for installing images will fail if there are insufficient global pages available in the system (for example, the number of global pages required to install the shared library in VMS/IRAF V2.10 is about 1267). If the system has insufficient free global pages to run the INSTALL.COM script one must either increase the number of system global pages (which requires rebooting the system), or one must edit the INSTALL.LST file to reduce the number of images to be installed.