5. FILES › 5.2 VTOC/Catalog Activity Information Area Files › 5.2.2 VSAM Data Set Allocation File (VCA_VS) › 5.2.2.3 VCA_VS Usage Considerations
5.2.2.3 VCA_VS Usage Considerations
This section identifies special considerations and techniques
related to using the VCA_VS file.
Relationship to Catalogs As Data Source
The data for this file is derived from catalog structures.
No VTOC data is present in the VCA_VS file. Actual data
sources for the VCA_VS observations are:
o ICF catalog structures
- the BCS component (also known as a user catalog)
- the VVDS component
o VSAM catalog structures
If you are still using pre-ICF catalog structures, then
suballocated data sets are possible objects unless the VSAM
data set was allocated with the UNIQUE keyword. Objects
suballocated within such an "old-style" catalog can only be
identified by means of the VCA_VS file.
The DETAIL timespan VCA_VS file has the same structure as
the VCADAA file, but contains detailed information describing
a VSAM Relative Record Data Set (RRDS), Entry Sequenced Data
Set (ESDS), Key Sequenced Data Set (KSDS), or Linear Data Set
(LDS).
A Transformation of LISTCAT Data
In many ways, the VCA_VS file can be viewed as the output of
IDCAMS LISTCAT transformed into a SAS file. It is literally
an inventory of the catalog structures at a given point in
time. There are several SAS data steps and PROC SORTs needed
to transform raw VCC data into a cycle of the VCA_VS file.
Effect of EXCLUDEVOL During Data Collection
Excluding volumes from VCC data collection can have an impact
on the content of the VCA_VS file. If a BCS exists on a
volume that is not scanned, then the BCS will also not be
scanned. If a BCS is not scanned, then only the VVDS
component of an ICF catalog structure contributes data toward
VCA_VS observations.
You may specify that VSAM data sets are/are not to be saved
in the VCA_VS file when there are no matching BCS records
collected. The BCSREQUIRED option is discussed in Chapter 7.
The default is to accept all VSAM data sets with records from
only the VVDS. When this happens, the VCC Processing Flags
(DAAPFLAG) are set to indicate the presence or absence of the
BCS record as follows:
'11......'B - BCS and VVDS elements are present
'01......'B - BCS elements are not present
We process the BCS to obtain the following data elements.
When the BCS records are not present, these data elements are
not valid in the VCA_VS file:
Element Title
-------- ---------------------------------
DAAOWNER VSAM Data Set Owner
DAABNAME Alternate Index Base Cluster Name
DAACFLAG VSAM Cluster Flags
DAASECUR Data Set Security
CREATEDT Creation Date
EXPDT Expiration Date
Of these, the most important to you might be the Creation
Date (CREATEDT) element. It may be used to compute the
DURATION element and could affect some data set charges
issued by the CA MICS Accounting and Chargeback product
(depending on your accounting journal file options).
Extra Observations When Extents Greater Than 16
Because a VSAM data set may have 128 extents and a VCA_VS
observation will (by design) only hold 16 extents, extra
(pseudo) observations will be created in both the VCADAA and
VCA_VS files to identify the additional VSAM data set
extents. DAARECNO is incremented by 1 for each extra
observation required. Consider this simple example:
DSNAME DAARECNO DAAEXTNO DAAXSZ01 DAAXTK01 ....
-------------------- -------- -------- -------- --------
USERID.VSAMTEST.DATA 1 44 15 10025
USERID.VSAMTEST.DATA 2 0 15 8085
USERID.VSAMTEST.DATA 3 0 15 12375
Each extra (pseudo) observation describes the next set of 16
extents. The extra observations take DASD space and time to
build, and are important only if you run the TRACK MAP
standard report or do very detailed extent reporting.
All accumulated elements in these pseudo observations
(DAASPACA, DAASPACU, DAACOST, etc.) are set to zero and will
not affect any summarizations. In the example above, DAAEXTNO
indicates 44 extents but that is only shown in the first
observation -- the extra observations have had the numeric
elements set to zero. Note also, that DAAXSZ01 in the
observation with DAARECNO set to 2 is describing the size of
extent 17 not extent 1. Likewise, the next observation
describes extent 33 under DAAXSZ01 rather than extent 1.
This data set is fully described in a total of 3 observations
(because 44 is less than 3 times 16). If the data set were in
49 extents, a fourth observation would be written for this
data set.
To save processing time and DASD space, you may specify that
the extra observations are to be deleted during the DAILY
DAY090 step. They may be deleted from either or both of the
VCADAA and VCA_VS files by coding EXTENTDETAIL fff NO and
running a VCAPGEN. See Chapter 7 for details.
Computation of Space Used For VSAM
While the VCADAA file is the definitive view of space
allocated for both non-VSAM and VSAM files, the VCA_VS file
offers the only accurate view of space used. The algorithm
used by VCA to compute space used for VSAM data sets is
complex. Elements involved in the calculations include:
Element Title
-------- ----------------------------------------
DAABYTCA Number of Bytes per CA
DAATKCA Number of Tracks per CA
DAAHURBA High-Used Relative Block Address (RBA)
DAACINV Control Interval Size
DAACIPCA Number of Control Intervals in a Control Area
Because system page type data sets (PLPA, Common, Page, etc.)
can use a special track overflow option not available to
other types of VSAM data sets, they may have a fractional
number of Control Intervals (CI) on a track (for example,
n.3, n.8). When this happens, the method VCA uses to
calculate space used is essential for accuracy.
Access Method Data Statistics and Attributes
An old-style VSAM Catalog or a VSAM Volume Data Set (VVDS) on
the primary (first used) volume contains the Access Method
Data Statistics Block (AMDSB) cell, which records information
pertaining to the whole VSAM data set. This set of elements
(approximately 40) must be propagated from the first volume
and/or first key range's AMDSB cell to all other volume
and/or key range observations.
An AMDSB Exception Report is generated on the DAILY step
DAY090 MICSLOG output when any AMDSB cell is not present.
This can happen when a VSAM catalog or primary VVDS is not
processed or is not excluded from collection.
For VSAM data sets allocated on multiple volumes, Key
Sequenced (KSDS) VSAM data sets split into multiple key
ranges, or KSDSs created with the IMBED option, the following
data elements are propagated:
Element Title
-------- ----------------------------------------
DAAATTR3 AMDSB Attributes
DAAATTRA AMDSB Data Set Attributes
DAABFNO Number of Data or Index Buffers
DAACINV VSAM Control Interval Size
DAACIPCA Number of CIs in a CA
DAAFSCA Number of Free CIs in a CA
DAAFSCI Number of Free Bytes in a CI
DAAHLRBA RBA of High Level Index Record
DAAKEYL Key Length
DAAMXLRC Maximum Record Size
DAANEXT Number of Extents in Data Set
DAAPCTCA Percentage of Free CIs in the CA
DAAPCTCI Percentage of Free Bytes in the CI
DAAREFDT Data Set Last Reference Date
DAARKP Relative Key Position
DAASSRBA RBA of First Sequence Set Record
DAASTRNO Number of Concurrent Requests
DAASTSP OS/VS System Timestamp
DAAASPA Number of Bytes of Free Space
DAADELR Number of Deleted Records
DAAEXCP Number of EXCPs
DAAIREC Number of Inserted Records
DAANCAS Number of CA Splits
DAANCIS Number of CI Splits
DAANEXT Number of Extents in Data Set
DAANIL Number of Index Levels
DAANLR Number of User-supplied Records
DAARETR Number of Retrieved Records
DAAUPR Number of Updated Records
These elements are copied from the Access Method Data
Statistics Block (AMDSB) information cell, collected from the
VSAM data set's primary volume VVDS, into all observations
defining the same VSAM data set. If the AMDSB cell is
missing (for example, the primary volume was excluded from
the Space Collector run or the volume processing failed), a
MICSLOG run time exception report is produced. Any VSAM data
sets on this report will contain the above elements set to
zero or missing. You should review the VCC run to determine
why the AMDSB was not collected.
The following elements are not part of the AMDSB cell but are
copied from the primary observation to ensure that all
observations for a VSAM data set are consistent:
Element Title
-------- ----------------------------------------
DAAALTYP Allocation Type
DAAATTR1 VSAM Data Set Attributes
DAABUFSZ VSAM Minimum Buffer Size
DAAPRIMS Primary Allocation
DAASCALO Secondary Allocation
DAASHROP Sharing Options
LRECL Data Set Logical Record Length
RECFM Data Set Record Format
STORDATC DFSMS Data Class Name
STORMGTC DFSMS Management Class Name
STORSTGC DFSMS Storage Class Name
DAALBKTS Managed Data Set Last Backup Timestamp
DAASMSID Number of System Managed Data Sets
Key Range Qualifier Suffix in DSNAME
Data set names (DSNAME) for VSAM data sets that have been
split into multiple key ranges contain the key range
qualifier suffix (.A001, .A002 etc.) for the Data and Index
components in the VCA_VS file.
For key range defined VSAM data sets, the DATA, INDEX, and
SSET component names (DSNAME) will be suffixed by a unique
four-character qualifier (a letter from A-Z followed by a
three-digit sequence number).
The IMBED Option and the DAAVCOMP Element
If a KSDS was defined with the IMBED option, there will be a
third set of observations (one per data component volume) to
define the imbedded sequence set (DAAVCOMP='SSET'). This
pseudo observation represents that portion of the data
component used to imbed the low level index record in the
first track of each control area. Because it is part of the
index, it will have the same data set name as the index
component.
Multi-Volume Effect On Reporting
To report on a VSAM data set from the VCA_VS file, you will
need to sort (and possibly summarize) by Catalog Name
(DAACATNM), Cluster Name (DAACNAME), Component Type
(DAAVCOMP), and Data Set Name (DSNAME) followed by Volume
Serial Number (VOLSER) to bring the component parts together.
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