While this is not quite the same thing as 2 CICS regions using a page of the same load module, take a look in Principles of Operation which talks about how "fork" is handled. From page 3-15 of August 2010 version of POP: The suppression-on-protection function is useful in performing the POSIX fork function, which causes a duplicate address space to be created. The following discussion pertains to when enhanced DAT does not apply, or when enhanced DAT applies but the format-control (FC) bit in the segment-table entry is zero. When forking occurs, the control program causes the same page of different address spaces to map to a single page frame of real storage as long as a store in the page is not attempted. Then, when a store is attempted in a particular address space, the control program assigns a unique page frame to the page in that address space and copies the contents of the page to the new page frame. This last action is sometimes called the copy-on-write function. The control program sets the DAT-protection bit to one in the page-table entry for a page in order to detect an attempt to store in the page. The control program may initially set the DAT-protection bit to one in a segment-table entry to detect an attempt to store anywhere in the specified segment.
regards, Joe D'Alessandro ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
