If the size of the user's virtual machine is defined below the end of the CMS nucle­
us (refer to label NUCSIGMA in Figure 35 CMS Storage Map 1), it is not possible
to IPL by device name. This is because the CMS nucleus is too large to be loaded
into the user's virtual storage. Therefore, the user can only IPL by system name (e.
g. IPL CMS). The loader table is placed immediately below the CMS nucleus. On the other hand, if the size of the user's virtual machine is defined above the
ending location of the CMS nucleus (refer to Figure 36 CMS Storage Map 2 and
Figure 37 CMS Storage Map 3), the user may IPL by either device name or system
name.
IPLing by device name:
The Sand Y-STAT, and the loader table are placed above the CMS nucleus.
If there isn't enough room to contain the Sand Y -STAT, they are placed in low
storage. Likewise, if there is insufficient room for the loader table above the CMS nucleus (NUCSIGMA), it is placed below the nucleus. Any leftover free
space above the nucleus is placed on the high DMSFREE chain.
IPLing by system name:
The shared copy of the Sand Y -STAT and nucleus is used. The loader table is
placed above the Sand Y -STAT (NUCOMEGA) if there is sufficient room. If
there is insufficient room to place the loader table above the Sand Y-STAT, it
is placed below the nucleus. Any leftover free space above the Sand Y -STAT (NUCOMEGA) is placed on the high DMSFREE chain.
Functional Information 319

'X'MB NUCOMEGA NUCSIGM/\ 'X'MB­
X'70000' NUCALPHA VIRTUAL STORAGE I S-STAT and Y-STAT (Shared) CMS Nucleus (Shared) OS Simulation, EXEC, EXEC 2, REXX, XEDIT, CMS interrupt handlers, file system, free storage
management, loader, device I/O, debug.
Storage Key X'F' or X'O'
END OF STORAGE VMSIZE System Loader Table (Size determined by set LDRTBLS command)
Storage Key X'F'
DMSFREE requests when no more low storage is available FREELOWE Storage Key X'E' or X'F'
--------------
Unused portion of User Program Area ..... MAINHIGH Storage Key X'E'
- ----------- --- GETMAIN requests
Storage Key X'E' MAINSTRT - - - - - - - - - - - - - -
X'20000' I X'10000'
X'EOOO' I X'5000'
X'O'
The User's Program (Program is located via the LOAD command)
Storage Key X'E'
Low Storage DMSFREE Nucleus Free Storage Area. The upper part of this area may contain the S-STAT and/or the Y-STAT, followed by the
FREETAB, if there is enough room.
Storage Key X'F'
Transient Program Area
Storage Key X'E'
Low Storage DMSFREE User Free Storage Area
Storage Key X'E' DMSNUC System Control Blocks, flags constants, and pointers
Storage Key X'F' * * The page starting at X'4000' containing OPSECT, SUBSECT, DBGSECT, DMSERL, TSOBLKS, USERSECT, and free
storage has a Storage Key X'E'. User Program Area CONTROL BLOCKS IN FREE STORAGE DECB II LDRST II AFT II ADT I CMSSAVE II CMSCB II FSTB I Figure 35. eMS Storage Map 1. CMS virtual storage usage when the CMS nucleus is larger than the user's virtual storage. In this case, you must
IPL by system name (VMSIZE is less than NUCSIGMA). Note: MAINHIGH is extended upward and FREEL OWE is extended downward. ·320 VM/SP System Programmer's Guide