This article describes a minimum MVS system, located on one disk, which will run JES, VTAM, TSO, and ISPF. By copying only the necessary files from your current system you need less than 200 cylinders of 3380 to constitute a mini MVS system. Such a system can be saved on one tape or cartridge.

It is mainly for safety. With a mini MVS system on disk you can re-IPL immediately in the case of a big crash on your present SYSRES (or on other important volumes) in order to be able to restore what has been damaged. Also, you avoid using DF/DSS stand-alone, which is two or three times slower than DF/DSS executing under MVS. If you have PR/SM (or its equivalent) installed, you can use a mini MVS system to test a new partition quickly.

Keeping a mini MVS system on tape preceded by the DF/DSS stand-alone program (rather than on DASD) enables you to restore it to disk immediately after IPLing from the 3420/3480 unit and entering the DF/DSS stand-alone parameters. This can help you substantially when you bring your system up on a back-up site. After restoring the mini MVS system, you log on and submit jobs to restore the remaining volumes. Eventually you can IPL on the restored system.

Of course, you will not create a clone of your production system, but only a small MVS to be used temporarily. All the files are the smallest possible (there are no SMF, STGINDEX, DUMPxx, or NCPLIB files). The only RACF/TSO user-id will be IBMUSER. At IPL time you must expect many messages and replies because of the lack of some system files or PARMLIB members.

The following steps create a mini MVS system with JES2, RACF, VTAM, TSO, and ISPF on a disk called MINMVS. The driving system is MVS/XA.

1 Initialize MINMVS with IPL text using ICKDSF.

2 Allocate MINI.PARMLIB, MINI.LOGREC, MINI.PROCLIB, MINI.UADS, MINI.BRODCAST, MINI.HASPCKPT, and MINI.HASPACE on it using IEFBR14. The size of this latter file will be 20 3380 cylinders. Allocate only a few tracks for the others.

3 Change the high-level identifier from MINI to SYS1 using IEHPROGM.

4 Using IDCAMS, define a USERCAT on MINMVS: it will be the future master catalog. You may optionally define all the aliases of your driving system in it.

5 Copy on MINMVS the main libraries of your current system. With DF/DSS, the SYSIN would be:

COPY DS(INCLUDE(SYS1.LINKLIB,
SYS1.LPALIB,SYS1.SVCLIB,SYS1.CMDLIB, -
SYS1.NUCLEUS,SYS1.VTAMLST,SYS1.VTAMLIB, -
ISR.**,ISP.**)) -
ODY(MINMVS) TOL (ENQF) WAIT(0,0) SHR

6 Update SYS1.NUCLEUS(SYSCATLG) on MINMVS using IEBGENER or IEBDG to indicate the new master catalog.

7 Define three page datasets: PLPA (10 cylinders), COMMON (5 cylinders), and LOCAL (30 cylinders).

8 Catalogue in the new master catalog all the files created in steps 2 and 5 using DEFINE NONVSAM. Also create an entry for SYS1.RACF.

9 Update the following members in your new SYS1.PARMLIB with IEBUPDTE,PARM=NEW:

- IEAAPF00 - SYS1.VTAMLIB MINMVS
- LNKLST00 - SYS1. LINKLIB and SYS1.CMDLIB
- IEASYS00 - APF=00,LNK=00,PAGE=, etc
- TSOKEY00 - no change

With MVS/XA 2.2.0 and above, you need a CONSOL00 ] member.

10 Update the following procedures in your new SYS1.PROCLIB:

- JES2 (with no user PROCLIB)
- NET (with only SYS1.VTAMLIB, SYS1.VTAMLST)
- IKJS - TSO LOGON procedure, with all ISPF files, and a temporary //ISPROF.
Code EXEC PGM=IKJEFT01, PARM=ISPF to invoke ISPF directly.

At IPL time, you will have to start JES2, NET, and TSO manually (you may create a COMMND00 member in PARMLIB in advance).

11 Transfer the following procedures from your current SYS1.PROCLIB: TSO, LLA, DUMPSRV, IEESYSAS, IEEVMPCR, and INIT

12 Transfer your current JES2PARM and modify it as follows:

SPOOLDEF ...,VOL=MINMVS,DSNAME=SYS1.HASPACE
CKPTDEF ....,VOL=MINMVS,DSNAME=SYS1.HASPCKPT

13 Create and initialize SYS1.RACF as follows:

// EXEC PGM=ICHMIN00,PARM=NEW
//SYSRACF DD DSN=SYS1.RACF,DISP=(NEW,KEEP),
// SPACE=(TRK,(30),,CONTIG),
// DCB=(RECFM=F,BLKSIZE=1024,DSORG=PSU)

14 Verify module IGC0001C CSECT IEAVTRML (memory termination table) in your new SYS1.LPALIB. Several products (eg RMF, IMS, NetView) ZAP it to indicate the name of their own routines. If these routines are not in SYS1.LPALIB but rather in LPALST libraries, you should ZAP it back to binary zeroes to avoid an S806 abend at IPL time.

15 Create the TSO user-id IBMUSER with the following batch TSO job:

// EXEC PGM=IKJEFT01
//SYSUADS DD DISP=SHR,DSN=SYS1.UADS,
// UNIT=3380,VOL=SER=MINMVS
//SYSTSPRT DD SYSOUT=*
//SYSTSIN DD *
ACCOUNT A (IBMUSER P A IKJS) JCL OPER ACCT NOMOUNT UNIT(SYSALLDA) END

16 Initialize the new SYS1.LOGREC using IFCDIP00. If you intend to keep your mini MVS system on tape, add the following two steps.

17 Copy SYS1.SAMPLIB(ADRDMPRS) onto file 1 of an NL tape, using LRECL=80,BLKSIZE=80,RECFM=F (DF/DSS stand-alone program)

18 Do a DF/DSS full dump of MINMVS onto file 2 of the tape.

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