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$CRMPSC and $CREATE services

The $CRMPSC system service creates a process-private or global section and maps it into process address space.The options or flags that determine its actions are described in the OpenVMS System Services Reference Manual

The $CREATE RMS service can be used to create a new file, or to open an existing file.The options and flags that determine its operation are described in the OpenVMS Record Management Services (RMS) Reference Manual.

The example code uses $CREATE with the User File Open (FAB$M_UFO) option and various file sharing options, and then uses $CRMPSC to map the contents of the file as a global section into image virtual address space (twice). The code then demonstrates some basic operations on the section: data is written into the first range of virtual address space where the section is mapped, and then read back in via the second range.

The $UPDSEC system service (not shown) would then be used at appropriate intervals; the call will flush the contents of the section from memory back to the backing storage file on disk.

For information on synchronizing and interlocking access to shared memory sections among multiple writing processes, see the data synchronization and lock manager synchronization chapters, as well as the memory management chapters, in the OpenVMS Programming Concepts manual.

» Code Example