IBM Virtual Machine Facility/370: Planning and System Generation Guide 2
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Planning Considerations for CMS You can write EXEC procedures to control the operation of a batch facility virtual machine. See the VM/J70 for examples of these EXEC procedures. Saving eMS CMS is designed so that it can be saved easily and so that the second segment of CMS can be shared by CMS users. Also, CMS is designed so that CMS/DOS, CMS VSAM and access method services, the CMS Editor, eMS EXEC processor, and CMS OS simulation routines can be placed in discontiguous saved segments. The VM/370 starter system has entries in the system name table (DMKSNT) and CP system control file (DMKSYS) so that you can save CMS (and the CMS discontiguous saved segments) at the end of the system generation procedure for eMS. For more information about saved systems, see the "Saved Systems" sect.ion of this mannal and. see the !M/370 30 IBM VM/370 Planning and System Generation
CMS VSAM and Access Method Services Planning Considerations for CMS VSAM and Access Method Services CMS supports interactive program development for using VSAM. CMS supports VSAM for as programs OS/VS COBOL, or as PL/I programming languages; or in DOS/VS COBOL or DOS PL/I programming languages. VSAM for as or nos assembler language programs. as and DOS programs written in VS BASIC, DOS programs written CMS does not support CMS also supports access method services to manipulate as and DOS VSAM and SAM data sets. Under CMS, VSAM data sets can span up to nine DASD volumes. CMS does not support VSAM data set sharing; however, CMS already supports the sharing of minidisks or full pack minidisks. Only one user may have write access to the VSAM master catalog, but many other users may read and reference the catalog at the same time. VSAM data sets created in CMS are not in the CMS file format. Therefore, CMS commands currently used to manipulate CMS files cannot be used for VSAM data sets that are read or written in CMS. A VSAM data set created in CMS has a file format that is exactly the same as, and therefore compatible with, as and DOS VSAM data sets. Thus a VSAM data set created in CMS can later be read or updated by as or DOS. Because VSAM data sets in CMS are not a part of the eMS file system, eMS file size, record length, and minidisk size restrictions do not apply. The VSAM data sets are manipulated with access method services programs executed under CMS, instead of with the eMS file system commands. Also, all VSAM minidisks and full packs used in eMS must be initialized with the IBCDASDI program or an appropriate DOS/VS or OS/VS disk initialization program (if the minidisk is a full pack); the eMS FORMAT command must not be used. In its support of VSAM data sets, eMS uses RPS (rotational position sensing) wherever possible. eMS does not use RPS for 2314/2319 devices, or for 3340 devices that do not have the feature. Hardware Devices Supported Because CMS support of VSAM data sets is based on DOS/VS VSAM and DOS/VS access method services, only disks supported by DOS/VS can be used for VSAM data sets in eMS or for CMS disk files used as input by access method services. These disks are: • IBM 2314 Direct Access Storage Facility • IBM 231Q Disk Storage • IBM 3330 Disk Storage, Models 1 and 2 • IBM 3330 Disk Storage, Model 11 • IBM 3340 Direct Access Storage Facility • IBM 3344 Direct Access storage Part 1. Planning for System Generation 31