Paqe of GC20-1807-7 As Updated April 1, 1981 by TNL GN25-0829
The format of an element on the GETMAIN free element chain is as
follows:
r I o (0) I 1 4 (4) , i i
FREPTR --pointer to next free
element in the chain, or 0 if there is no next element
---i I 1---- FRELEN --length, in bytes, of
this element
-----i i 1------- Remainder of this free element
The amount of storage reserved for eMS use is determined at eMS IPL
time based on the size of the virtual machine. The formula for
calculating this reserved storage is:
Less than 512K
512K
Greater than 512K 10 pages
12 pages + 2 pages for each
256K in excess of 512K
12 pages + 2 pages for each
256K in excess of 512K
246 IBM VM/370 System Programmer's Guide

Page of GC20-1807-7 As Updated April 1, 1981 by TNL GN25-0829 DMSFREE FREE STORAGE MANAGEMENT
The DMSFREE macro allocates CMS free storage. The format of the DMSFREE macro is: r r label] DMSFREE r , DWORDS= { n } I, MIN= { n } I (0) I (1) I L .J r r "r .. " II I,ERR=lladdrl I I NUCLEUS I I I I * I I L L .J.J L L J.J r r" I ,AREA= ILOW II I IHIGHII L L.J.J r .." I I I BALRII L L.J.J L- __ _
label
is any valid assembler language label. DW ORDS={ n } (0) MIN= { n }
(1)
is the number of doublewords of free storage requested. DWORDS=n specifies the number of doublewords directly and DWORDS=(O) indicates that register 0 contains the number of
doublewords requested. Do not specify any register other than
register o. CMS returns, in register 0, the number of doublewords
allocated in register 1, the address of the first byte of
allocated storage.
indicates a variable request for free storage. If the exact
number of doublewords indicated by the DWORDS operand is not
available, then the largest block of storage that is greater
than or equal to the minimum is returned. KIN=n specifies the
minimum number of doublewords of free storage directly while
MIN=(1) indicates that the minimum is in register 1. tio not
specify any register other than register 1.
r , TY PE= I I INUCLEUSI L J
indicates the type of CMS storage with which this request for
free storage is filled: USER or NUCLEUS. r ,
ER R= Iladdr I I * I L J is--·t--h--e ---r.e-turnad-d·r-ess- i·f a-uJ- occUrs. "l-addr-'-' is address that can be referred to in an LA (load address)
instruction. The error return is taken if there is a macro
coding error or if there is not enough free storage available
to fill the request. If the asterisk (*) is specified for the
return address, the error return is the same as a normal Part 3. Conversational Konitor System (CMS) 247