To me, this sounds like a task that is tailor made for iSeries Journaling. Rather than trying to serialize the file access, just use the system to journal the change and then run a daily job to retrieve, analyze, report, and clean out the Journal log. The techniques and methods for doing all this are well known and well supported. :)
If you really need serialized access, as in normal file locking won't work, you might want to look at CICS, which excels at doing just that, making each file operation absolutely atomic while preserving the appearance of concurrent access.
Else, if you are just looking for a temporary, or a "quick and dirty" solution, what you are suggesting should work okay. Look up techniques for "optimistic record locking" on Google for a bunch of ideas of how to do what you are thinking of. Optimistic locking has to do exactly the process you are describing.
Hope that helps just a bit. Very interesting question, please post how you do decide to resolve it.
Yours
-Paul
On Aug 01, 2014, at 07:52 AM, "(WalzCraft) Jerry Forss" <JForss@xxxxxxxxxxxxx> wrote:
Hi All,
I want to create a "new" standard here in which all access to a file (Inquiry and Update) are done through a single pgm.
Let's call it FMMasterR for file MASTER.
My display pgm gets the record from FMMasterR. It is maintained and returned to FMMasterR as a DS (Parm_DS). I chain to MASTER receiving it into a Old_DS. I can compare Parm_DS to Old_DS to see that something changed. I can get the field names in the file easy enough loading into an array. What I want to do spin through the fields finding what changed. Something like
If Parm_DS.Field(1) < > Old_DS.Field(1). I then can write to a maintenance log of specific field changes. I know someone does field level maintenance logging so I am looking for some guidance on the best approach. Being I have the fields, length and pos I suppose I could try and compare doing a substring on the entire length of the file.
I am just playing and trying to come up with some ideas.
Thanks!!
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