The following are the storage attributes of records:
Storage attributes of records
1. Length : Records can either be stored as fixed length or variable length
1a. Fixed length: The whole record instance is persisted in a contiguous block of memory on the line
1b. Variable length: The root part of the record is persisted on the current line. The remaining part of the record is persisted on some other part of the memory.
Distinguish among erase, erase permanent, erase selective and erase all?
Erase cancels the membership of a record in specific set occurrences and removes only the named record.
Erase permanent removes the specific record and all mandatory occurrences it owns. It disconnects all optional members.
Erase selective removes the record, all mandatory members and all optional members not connected to other sets. It disconnects those that are connected.
Erase all removes the specified record and all the mandatory and optional records it owns.
Explain about Keep Long term.
Heavily accessed information might use this feature.
The storage of information can be allocated for long term.
The storage can be released explicitly by a valid program request.
This option is apt for relatively small amounts of information, as storage is obtained from large storage pool.
KEPT storage is properly maintained on the same logical terminal.
Storage pool data would not be preserved from one execution of IDMS-DC to another.
What is autostatus in IDMS?
Autostatus is a protocol mode which causes the expansion of each DML statement to include a 'perform IDMS-Status' statement.
Difference between Fixed length and Variable length records
o Fixed length records access is faster
o Variable length records maintains better utilization of space
2. Compressed : Records can be stored as compressed or uncompressed format
2a. Compressed : The record’s data can be compressed upto 50%
2b. Uncompressed: The records are represented as they are.