IBM OS/390 User Manual

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As it is desirable from both performance and integrity perspectives to separate
user data sets into several user catalogs, it is critical that data set names be
defined with the above information in mind. If, for example, all data set names
begin with CUSTOMER as the first node, then all the data sets will be defined in
only one user catalog. If the high order node for some data sets is PAYROLL,
and for others INVENTRY, then these data sets could be split between two user
catalogs if desired.
It is strongly recommended that data set naming conventions be defined
carefully and that they be enforced through training and review procedures
during conversion and after the system has been placed into production.
As data set naming conventions can greatly simplify the operation of your
OS/390 system, and can also make the migration process simpler, we have
included a separate chapter on recommendations for data set naming. See the
chapter, 25.4, “Set Up Standards, Procedures, and Documentation” on page 407,
for more information.
5.3 Storage and Space Management
5.3.1 VSE Considerations
Standard VSE system facilities provide for user management of DASD space
resources, or for VSAM management of DASD space for SAM files. Many VSE
users have OEM vendor disk space management packages, and/or tape library
management packages. User management requires manual procedures to
maintain catalogs of disk space in use or available, as well as tape volumes in
use, and the relationships between tape files and tape volumes. VSE users who
have not automated some or all of these functions find manual procedures error
prone and slow.
5.3.2 OS/390 Considerations
OS/390
s Direct Access Device Storage Manager (DADSM) and Data Facility --
System Managed Storage (DFSMS) components provide all the capabilities of
the VSE system, plus OEM vendor enhancements.
5.3.3 System Managed Storage
System-managed storage is the OS/390 automated approach to managing your
system
s storage resources. It uses software programs to manage data security,
placement, migration, backup, recall, recovery, and deletion to ensure that
current data is available when needed, and obsolete data is removed from
storage. The combination of system-managed storage and related hardware and
software products is called the DFSMS environment.
With DFSMS, you tailor the system-managed storage environment to your needs.
You define the requirements for performance, security, and availability, along
with storage management policies used to automatically manage the direct
access, tape, and optical devices used by the OS/390 operating systems. The
Interactive Storage Management Facility (ISMF), a component of DFSMSdfp,
provides the user interface for defining and maintaining these policies and the
Storage Management Subsystem (SMS) governs these policies for the system. In
this environment, RACF and DFSORT compliment the functions of the base
operating system. The following are brief descriptions of the DFSMS/MVS
100
VSE to OS/390 Migration Workbook