Root addressable area and IOVF processing
In root addressable area and IOVF processing, OPC deblocks each CI into its component parts (that is, segments, scraps, and FSEs).
It does this by starting at offset 8 and continuing until the end of CI, by incrementing the offset by the length of the item. During the deblocking process, the total lengths of all FSEs, scraps, and segments are accumulated.
After a CI is deblocked, the program chases the FSE chain and totals the number and length of FSEs. If this value differs from the value calculated during the deblocking process, a DEDB integrity problem has been detected. This test finds FSEs within segments, or segments within FSEs. OPC also verifies that the total of segment lengths, plus total scrap and FSE lengths, plus VSAM and IMS overhead, equals CI size.
Three output files are created:
- Area and free space information
- Segment information for all segments that reside in the Root Addressable part of an area
- Segment information for segments in IOVF and SDEP, and pointer information
The record types generated are as follows:
- Type
- Purpose
- 1,0
- Contains area definition information from the DMB (one record per area)
- 1,1
- Contains segment definition information from the DMB (four segments per record)
- 2,F
- Contains the length and location of each FSE or scrap encountered (one per FSE, no record generated for empty DOVF or IOVF CIs)
- 2,R
- Contains a count of the number of references to other CIs in the area (one per CI that has external references)
- 2,T
- Contains total free space in each of the component parts of the area (one record per area)
- 3,C
- Contains the RBA of all nonzero pointers: subtype 0 = RAP pointer,
1 = PTF pointer, 2 = PCF pointer, 3 = PCL pointer, 4 = SSP pointer (one per nonzero pointer)
- 3,S
- Contains the RBA and length of all segments (one per segment)
- 4,P
- Contains the RBA of all nonzero SDEP pointers (one per nonzero SDEP pointer)
- 4,S
- Contains the RBA of all SDEP segments (one per SDEP segment)
OPC ends abnormally if integrity errors or invalid VSAM CIDF and RDF fields are encountered in more CIs for the area being analyzed than the number specified for MAXERROR.