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- ALTERNATEINDEX
- Defines
an alternate index or re-catalogs an alternate index entry.
The
ALTERNATEINDEX keyword is followed by the parameters for the alternate
index as a whole. These parameters are enclosed in parentheses and,
optionally, are followed by parameters given separately for the DATA
and INDEX components.
Abbreviation: AIX®
- NAME(entryname)
- The
alternate index's entryname or the name of each of its components.
The entry name specified for the alternate index as a whole is not
propagated to the alternate index's components.
You can define
a separate entry name for the alternate index, its data component,
and its index component. If you do not give a name for the data or
index component, one is generated. For more information about the
system-generated name format, see z/OS DFSMS Managing Catalogs.
When
the alternate index, data component, and index component are individually
named, each can be addressed.
- RELATE(entryname)
- Names
the alternate index base cluster. The base cluster is an entry-sequenced
cluster or a key-sequenced cluster to which the alternate index is
to be related. You cannot relate an alternate index
to a reusable cluster, to a fixed-length or variable-length RRDS,
an extended addressable ESDS, a catalog, a VVDS (data set name 'SYS1.VVDS.Vvolser'),
another alternate index, a linear data set, or a non-VSAM data set. An
SMS-managed alternate index has the same management class and storage
class as its base cluster.
Select the entryname so
that the multilevel alias facility selects the same catalog as the
one containing the related data set name.
Abbreviation:
REL
- CYLINDERS(primary[
secondary])|
- KILOBYTES(primary[
secondary])|
- MEGABYTES(primary[
secondary])|
- RECORDS(primary[
secondary])|
- TRACKS(primary[
secondary])
- The
amount of space in cylinders, kilobytes, megabytes, records, or tracks
allocated to the alternate index from the volume's available space.
A kilobyte and megabyte allocation resolves to either tracks or cylinders;
records are allocated to the nearest track boundary.
Exception: If
allocation resolves to tracks, the space is contiguous. For more information,
see “Optimizing Control Area Size” in z/OS DFSMS Using Data Sets.
Requests
for space are directed to DADSM and result in a format-1 DSCB for
the data and index component entries.
If you do not use the
MODEL parameter or the RECATALOG parameter, you must include one,
and only one, of these parameters: CYLINDERS, KILOBYTES, MEGABYTES,
RECORDS, or TRACKS.
The space parameter is optional if the
cluster is SMS-managed, but if you do not use it, space can be modeled
or defaulted by SMS. If it is not determined, the DEFINE is unsuccessful. The maximum space can be specified with unit of KILOBYTES
or MEGABYTES is 16,777,215. If the amount requested exceeds this value,
you should specify a different larger allocation unit.
To
maintain device independence, do not use the TRACKS or CYLINDERS parameters.
If you do not use TRACKS or CYLINDERS for an SMS-managed alternate
index, space is allocated on the volume selected by SMS.
When
you do not divide the data component into key ranges, and more than
one volume is given, the primary amount of space is allocated only
on the first volume when the component is defined. When the component
increases to extend to additional volumes, the first allocation on
each overflow volume is the primary amount.
Secondary amounts
can be allocated on all volumes available to contain parts of the
alternate index, regardless of the key ranges when the alternate index
is extended.
You can include the amount of space as a parameter
of ALTERNATEINDEX, as a parameter of DATA, or as a parameter of both
DATA and INDEX. - If the space is specified as a parameter of ALTERNATEINDEX, the
amount specified is divided between the data and index components.
The division algorithm is a function of control interval size, record
size, device type, and other data set attributes.
If the division
results in an allocation for the data component that is not an integral
multiple of the required control area size, the data component's allocation
is rounded up to the next higher control area multiple. This rounding
can result in a larger total allocation for your alternate index than
what you specified.
- If the space is specified as a parameter of DATA, the entire amount
given is allocated to the data component. An additional amount of
space, depending on control interval size, record size, device type,
and other data set attributes, is allocated to the index component.
To determine the exact amount of space allocated to
each component, list the alternate index's catalog entry, using the
LISTCAT command.
The primary and each secondary allocation
must be able to be satisfied within five extents;
otherwise, your DEFINE or data set extension is unsuccessful.
You
can use these keywords for both SMS managed and non-SMS-managed data
sets. - primary
- Allocates the initial amount of space to the alternate index.
- secondary
- Allocates the amount of space each time the alternate index extends,
as a secondary extent. If the secondary space allocation is greater
than 4.0 gigabytes, it is reduced to an amount as close to 4.0 GB
as possible, without going over. This is not true for extended addressability
data sets, which have no such space limitation. When you use secondary,
space for the alternate index's data and index components can be expanded
to a maximum of 123 extents.
Abbreviations: CYL, KB, MB, REC,
and TRK
- VOLUMES(volser[
volser...])
- Specifies
the volumes on which an alternate index's components are to have space.
This parameter is not required if the cluster is modeled or if the
cluster is SMS-managed. You can specify VOLUMES for SMS-managed data
sets; however, the volumes specified might not be used and, in some
cases, can result in an error.
For SMS-managed data sets, you
can use up to 59 volumes. If the combined number of volumes for a
cluster and its associated alternate indexes exceeds 59, unpredictable
results can occur.
You can let SMS choose the volumes for
SMS-managed data sets by coding an * for the volser with the VOLUMES
parameter. If both user-specified and SMS-specified volumes are requested,
the user-specified volser must be input first in the command syntax.
The default is one volume.
If you do not use the MODEL parameter,
VOLUMES must be placed as a parameter of ALTERNATEINDEX, or as a parameter
of both DATA and INDEX.
If the data and index components are
to reside on different device types, you must include VOLUMES as a
parameter of both DATA and INDEX. If more than one volume is listed
with a single VOLUMES parameter, the volumes must be the same device
type.
You can repeat a volume serial number in the list only
if you use the KEYRANGE parameter. This can place more than one key
range on the same volume. However, repetition is valid only if all
duplicate occurrences are used for the primary allocation of some
key range.
The VOLUMES parameter interacts with other DEFINE
ALTERNATEINDEX parameters. Ensure that the volumes you define for
the alternate index are consistent with the alternate index's other
attributes: - CYLINDERS, RECORDS, TRACKS: The volumes contain enough available
space to satisfy the component's primary space requirement.
- FILE: To define an alternate index, the volume information supplied
with the DD statement pointed to by FILE must be consistent with the
information listed for the alternate index and its components.
Abbreviation: VOL
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