Know IDMS?
Do you think this would be a good question when interviewing an IDMS DBA?
Theme – Database Design: big pages, small records
An application programmer comes into your office and says “I am getting an IDMS 1211 return code, but the area is only at 60% full”. What’s your course of action?
Do you think this would be a good question when interviewing an IDMS DBA?
Theme – Database Design: big pages, small records
An application programmer comes into your office and says “I am getting an IDMS 1211 return code, but the area is only at 60% full”. What’s your course of action?
This most likely occurs when a page is logically full. With the default database key format of 3 bytes for page number and one byte for line index, the maximum number of records is 255. With a large page size and an area with a lot of small records, it is possible that 255 times the average record size is smaller than the page size. With the maximum number of line indexes met, the page is full even though the Area may be at 60% capacity.
Most DBA’s, in a non-emergency situation will perform an unload and reload of the area after determining the proper page size and number of pages.
Review your record sizes – determine your average record size for any records that are fixed or compressed
Determine Space Requirements – consider your record size, estimated record occurrences, growth factor and reserve space
Look for similar problems – if your estimates were off for this Area, review your other Areas and review your assumptions that led to your page size and number of pages
Unload / Reload – Consider an unload and reload of the Area with the proper page size and number of pages
Test CV first – don’t wing it, run the process in the Test CV first
Remember – your only as good as your last backup
