This topic covers the following subtopics.
When you allocate or define a data set to use SMS, you specify
your data set requirements by using a data class, a storage class,
and a management class. Typically, you do not need to specify these
classes because a storage administrator has set up automatic class
selection (ACS) routines to determine which classes to use for a data
set.
Descriptions of the classes follow:
- A
data class is a named list of data set allocation and space attributes
that SMS assigns to a data set when it is allocated. You can also
use a data class with a non-system-managed data set.
- A storage class
is a named list of data set service or performance objectives that
SMS uses to identify performance and availability requirements for
data sets. The object access method (OAM) uses storage classes to
control the placement of objects in an object storage hierarchy. Each
data set has a storage class if and only if the data set is SMS-managed.
- A management class is a named list of
management attributes that DFSMShsm uses to control action for retention,
migration, backup, and release of allocated but unused space in data
sets. OAM uses management classes to control action for the retention,
backup, and class transition of objects in an object storage hierarchy. DFSMSrmm can
use the management class name assigned to a tape data set to identify
a policy which should be used to manage the data set. For non-system-managed
tape data sets, DFSMSrmm calls the management class ACS routine. See z/OS DFSMSrmm Implementation and Customization Guide.
Your
storage administrator defines the attributes of each class in an SMS
configuration. An SMS configuration is a complete set of definitions,
ACS routines, and other system information SMS uses to manage your
data sets. The definitions group data sets according to common characteristics.
As you allocate new data sets, the ACS routines assign those characteristics.
With the information contained in the SMS configuration, SMS manages
your data sets most effectively with a knowledgeable use of the available
hardware. See z/OS DFSMSdfp Storage Administration for
information about using SMS classes and managing data sets and volumes.
The
Storage Management Subsystem (SMS) can manage tape data sets on native
volumes in a tape library and on the logical volumes in a Virtual
Tape Server (VTS). DFSMSrmm provides some services for the stacked
volumes contained in a Virtual Tape Server. See z/OS DFSMSrmm Implementation and Customization Guide.
Some
requirements for using SMS follow:
- Extended-format data sets and compressed-format data sets must
be system managed.
- SMS must be active when you allocate a new data set to be SMS
managed.
- Your storage administrator must be aware
that ACS routines are used for data sets created with distributed
file manager (DFM). These data sets must be system managed. If the
storage class ACS routine does not assign a storage class, distributed
file manager deletes the just-created data set, because distributed
file manager does not create non-system-managed data sets. Distributed
file manager does, however, access non-system-managed data sets.
Table 1 lists the storage management functions
and products you can use with system-managed and non-system-managed
data sets. For details, see z/OS DFSMSdfp Storage Administration.
Table 1. Data set
activity for non-system-managed and system-managed data sets| Activity Allocation |
Non-System-Managed Data |
System-Managed Data |
|---|
| Data placement |
JCL, storage pools |
ACS, storage groups |
| Allocation control |
Software user installation
exits |
ACS |
| Allocation authorization,
definition |
RACF3, JCL, IDCAMS, TSO/E, DYNALLOC |
RACF3, data class, JCL, IDCAMS, TSO/E,
DYNALLOC |
|
Access:
|
|
|
| Access authorization |
RACF3 |
RACF3 |
| Read/write performance,
availability |
Manual placement, JCL,
DFSMSdss1, DFSMShsm2 |
Management and storage
class |
| Access method access to
UNIX byte stream |
JCL (PATH=) or dynamic
allocation equivalent |
JCL (PATH=) or dynamic
allocation equivalent |
|
Space Management:
|
|
|
| Backup |
DFSMShsm2, DFSMSdss1,
utilities |
Management class |
| Expiration |
JCL |
Management class |
| Release unused space |
DFSMSdss1, JCL |
Management class, JCL |
| Deletion |
DFSMShsm2, JCL, utilities |
Management class, JCL |
| Migration |
DFSMShsm2 |
Data and management class,
JCL |
Notes: - DFSMSdss: Moves data (dump, restore, copy, and move)
between volumes on DASD devices, manages space, and converts data
sets or volumes to SMS control. See z/OS DFSMSdss Storage Administration for
information about using DFSMSdss.
- DFSMShsm: Manages space, migrates data, and backs
up data through SMS classes and groups. See z/OS DFSMShsm Managing Your Own Data for
information about using DFSMShsm.
- RACF: Controls access to data sets and use of system
facilities.
|
The following
types of data sets cannot be system managed:
- Data sets having the same name as an already cataloged data set
- DASD data sets not cataloged
- Unmovable data sets (DSORG is xxU) except when set by a
checkpoint function
- Data sets with absolute track allocations
(ABSTR value for SPACE parameter on DD statement)
- Tape data sets
- Spooled data sets
Direct data sets (BDAM) can be system-managed but if a program
uses OPTCD=A, the program might become dependent on where the data
set is on the disk. For example, the program might record the cylinder
and head numbers in a data set. Such a data set should not be migrated
or moved. You can specify a management class that prevents automatic
migration.
Tape volumes in a system-managed tape library can be managed as
system-managed storage classes.
z/OS DFSMS Using Data Sets
Copyright IBM Corporation 1990, 2014