File Level identifier Vs. Record Format Level Identifier vs. Member level identifier

20 pts.
Tags:
as400/DB2
File Level Identifier
member level identifier
Record Format Level Identifier
Hi,

 

Please let me know the difference b/n File Level identifier, Record Format Level Identifier and Member level identifier with an example

ASKED: May 13, 2010  10:18 AM
UPDATED: May 13, 2010  9:33 PM

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File Level Identifier will have created Time stamp Value. Format Level Identifiers will have system created value. This will be used in programs to check the format of the file. I dont think there is no member identifier. Please correct me if i am wrong

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File and Member Level Identifiers are forms of timestamps that relate to creation date/time. But note that this can be different from the basic object creation date/time. That is, if you materially change the file definition through some interface such as SQL ALTER TABLE or similar means, the File Level Identifier will reflect the date/time of the last such change, while the object creation date/time will be unchanged.

Record Format Level Identifiers are essentially hashes of attributes of all of the fields in the format. Attributes such as lengths and buffer positions are hashed in order to generate a nearly unique value. This value can be used by programs to verify that the descriptions of record buffers that are compiled into the programs still match with the descriptions of the buffers of the files that are opened by those programs.

A difference between Format Level Identifiers in a program and in a file will result in a “level check” exception when the program attempts to open the file. This helps prevent programs from processing files that aren’t defined in the ways that programs expect them to be.

File/Member Level Identifiers are used by operations such as RSTOBJ to help avoid restoring files that are the wrong versions and destroying altered objects.

All types of level mismatches can be overridden when necessary.

Tom

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