This call accesses shared memory allocated by a DosAllocSeg or DosAllocHuge call.
DosGetSeg
Selector (SEL) - input
A process may issue DosAllocSeg or DosAllocHuge to allocate shareable segments of memory. The segment may be shareable through DosGiveSeg or DosGetSeg. If the segment is shareable through DosGetSeg, then the process that allocated the memory must pass the selector of the segment to the recipient process using some means of interprocess communication.
If at the time the shared segment is allocated, it is also specified as discardable, it is automatically locked for access by the caller. The caller may free the segment for discard by a DosUnlockSeg call. A process that gains access to the discardable shared segment by calling DosGetSeg has to lock the segment with a DosLockSeg request. However, DosLockSeg may return an error, indicating the segment is already locked. In this case, the process calls DosUnlockSeg repetitively, until the segment is fully unlocked. The process then locks the segment for its own use. Locking is an attribute of the segment, not the processes using the segment.
To access named shared memory allocated with a DosAllocShrSeg request, a process issues DosGetShrSeg.