Size of IMS catalog data sets
Before creating the data sets for an IMS catalog, run the IMS Catalog Populate utility (DFS3PU00) in the analysis-only mode to determine the approximate storage requirements of the data sets on your DASD devices.
In analysis-only mode, the DFS3PU00 utility calculates of the approximate size of the IMS catalog data sets by analyzing the contents of the ACB libraries that you provide as input to the utility. In analysis-only mode, the DFS3PU00 utility does not create the IMS catalog data sets.
The calculations of the utility do not include the data sets of the IMS directory, which is an extension of the IMS catalog that is used only when the IMS management of ACBs is enabled. The IMS directory is a system-managed replacement of the ACB libraries. If an IMS directory contained the same ACBs as an ACB library, the data sets of IMS directory might require only slightly more storage than the data sets of the ACB library. If the existing data sets of the IMS directory reach their capacity, IMS creates a new data set automatically to accommodate the growth. When IMS adds a data set, the IMS directory uses more storage.
To run the DFS3PU00 utility in analysis-only mode, specify DFSCP000 as the PSB for the utility in the utility JCL.
After the utility evaluates the members in your ACB libraries, it produces a report. This report is the same report that the DFS3PU00 utility produces when it loads the IMS catalog.
The first two sections provide statistics about the segments that would be inserted in the IMS catalog if it were loaded from the current input ACB libraries. The rest of the sections provide the storage estimates.
For the OSAM data sets, the storage sections of the report show the number of blocks of the specified size. For the VSAM KSDSs, which include the indirect list data set (ILDS), the primary index data set, and the secondary index data set, the report shows the number of VSAM records.
These numbers are estimates that reflect the amount of space needed to load the catalog records that are built from the ACB libraries that you provide as input to the DFS3PU00 utility. If you are calculating the amount of storage required for the IMS catalog data sets, provide plenty of additional space in your calculations to allow for expansion.
If you have IMS create the IMS catalog data sets automatically, you can specify additional space as a percentage of the estimates that are provided by the utility on the SPACEALLOC parameter in the IMS catalog section of the DFSDFxxx PROCLIB member. The default value for this parameter is 500%.
- DSG
- Data set group
- L
- A HALDB ILDS data set. The number of records shown represent the potential number of indirect list entries (ILEs) that could be created if the IMS catalog is reorganized.
- SC
- Segment code. When loading a segment type, IMS assigns a segment code as a unique identifier (an integer from 1 to 255). IMS assigns numbers in ascending sequence, starting with the root segment type (number 1) and continuing through all dependent segment types in hierarchical sequence.
- SEGS
- Segments
- X
- HALDB partitioned primary index.
CATALOG DFSCD000
PARTITION DFSCD01
NUMBER OF SEGMENTS INSERTED INTO THE CATALOG
INSERTED AVERAGE
SC SEGMENT SEGMENTS DSG PARENT SEGS/PARENT
-- -------- -------- --- -------- -----------
1 HEADER 4228 A
2 DBD 2530 A HEADER 0.6
3 CAPXDBD 7 D DBD 0.0
5 DSET 2599 D DBD 1.0
7 AREA 139 D DBD 0.1
9 SEGM 16337 B DBD 6.5
10 CAPXSEGM 1 D SEGM 0.0
12 FLD 16426 C SEGM 1.0
14 MAR 16426 C FLD 1.0
17 LCHILD 2687 B SEGM 0.2
20 XDFLD 134 B LCHILD 0.0
33 PSB 1840 A HEADER 0.4
35 PCB 9190 B PSB 5.0
37 SS 75274 B PCB 8.2
39 SF 1105 B SS 0.0
41 DBDXREF 8886 D PSB 4.8
WITHIN DUPLICATES
EXISTING NOT
SEGMENT HEADER INSERTED
------- -------- ----------
DBD 71 0
PSB 72 0
ESTIMATED SPACE REQUIREMENT TO HOLD INSERTED SEGMENTS
DSG BLKSIZE BLOCKS
--- ------- ------
A 4096 596
B 4096 9343
C 4096 8214
D 4096 236
DSG RECORDS
--- -------
L 8886
X 4230
SECONDARY
INDEX RECORDS
--------- -------
DFSCX000 8886