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Karthigaiselvan
New User
Joined: 11 Dec 2006
Posts: 35
Location: India
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Hi,
My IMS DB structure is as follows.
Order
- Item
- Message
where Order is root segment and Item, Message are both child segments of Order.
My program currently reads all Messages of an order using GNP calls in a loop & setting the parentage at Order.
For a new requirement, before doing the above process of reading all messages of an order, i need to read all the items of the order, process them & update a field in Order segment. So i am inserting the following calls before reading Messages -
1. Make a GU call to fetch the 1st item of the order by setting the parentage at Order.
2. Make GNP calls successively to fetch all items of the order and process.
3. Update the field in Order segment using GHU & REPL successively.
Now my questions are
1. How will the existing calls for reading message segments of the order work as the parentage would have been cancelled / lost by GHU call i made?
2. Or do i need to make another GU call with parentage at Order after REPL call?
3.Is there any other way to achieve this with out affecting the existing calls? |
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Sandy Zimmer
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Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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| Use multiple positioning. Set up your PSB with 2 views of the order. Use the first PCB to do your sequential processing. Then use the 2nd PCB to do your qualified GHU and subsequent REPL. |
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rajabhushanam.y
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Joined: 12 Jul 2007
Posts: 11
Location: Mysore
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Hi , why don't you use set the parentage ,before using the call ( p . path command) , it is my thinking only.
Cheers,
Rajabhushanam.y |
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Sandy Zimmer
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Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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Hi rajabhushanam,
There is absolutely no reason to issue path calls. As a matter of fact, it would be a lot more tricky. When getting a not found, you would then need to interrogate the keyfeedback area for last successful retrieval. Your POSITION would then be lost. Remember that in IMS, you are positioned at your last successful call. Using a qualified root, unqualified child ssa calls on your first PCB1 - then retrieving the parent with a qualified call on PCB2 would do the trick. When setting up your PSB - make sure PCB1 only allows get calls and PCB2 allows update calls. |
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Karthigaiselvan
New User
Joined: 11 Dec 2006
Posts: 35
Location: India
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Hi,
Thanks for all the replies. Though Multiple Positioning should work out for this case, we settled with a simple option of making another GU call with parentage command after processing the Item segments and before reading the Message segments. |
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Sandy Zimmer
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Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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| Why are you setting parentage? Did I miss something? |
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Bitneuker
CICS Moderator
Joined: 07 Nov 2005
Posts: 1104
Location: The Netherlands at Hole 19
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Well may be command codes are used  |
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Sandy Zimmer
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Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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| Yes, "D", but why? |
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Karthigaiselvan
New User
Joined: 11 Dec 2006
Posts: 35
Location: India
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Hi Sandy,
We set the parentage by command code 'P' right? D is for a path call.
The reason why i had to set the parentage was -
There were successive GNP calls already coded to read Messages of an order, I had to insert my new changes to process Items of an order before GNP & after 1st GU of root segment (Order). Please refer my 1st post for more details. So for GNP calls that follow my changes, i need to set the parentage as the parentage set earlier would be lost becasue of GHU made befroe that. Does that make sense? |
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Sandy Zimmer
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Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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You are correct about the command code. There are always multiple ways to do calls. If you want to leave the code as is and it is correct and efficient - then go for it!
I always like to think of the person maintaining or enchancing something I have done. Please tell me again why you need to set parentage? Can you accomplish the same thing with mulitple qualified ssa's beneath that parent? |
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Karthigaiselvan
New User
Joined: 11 Dec 2006
Posts: 35
Location: India
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Beneath the parent (order), i had to access ALL Item & Message segments (child) in sequence. So i can not use qualified SSAs for accessing the child segments under the parent.
I am not sure about the advantage of Multiple Qualified SSA. Could you please explain me this with an example? |
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Sandy Zimmer
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Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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Yes - you can use qualifed and non qualified SSAs to retrieve child segments. I am assuming that Item and Message are 2nd level child segments beneath an order. If the message turns out to be a child segment beneath the ITEM, it is easy to change the code. Take a quick look at your DBD.
1. GU call for ORDER segment - Qual SSA for ORDER. If you are going thru a database sequentially retrieving all ORDERs, then just load the retrieved ORDER number into the qualifed SSA for the ORDER that you have.
1.1. Perfrom a routine that will GN call for ITEM segment - Qual SSA for ORDER, Unqual SSA for ITEM- until no more ITEM segments for that ORDER - could be 1 - could be many. Check IMS status code for blanks after each call.
1.2. Perfrom a routine that will GN call for MESSAGE segment - Qual SSA for ORDER, Unqual SSA for MESSAGE - until no more MESSAGE segments for that ORDER- could be 1 - could be many. Check IMS status code for blanks after each call. |
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Karthigaiselvan
New User
Joined: 11 Dec 2006
Posts: 35
Location: India
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Ok. I understand that.
Items & Messages are 2nd level child segments only.
But in the existing code, there is already GNP call coded for retrieving Message segments. If i dont want to disturb that, then i can not go with option you suggested right? So I am setting the parentage since the GNP call will expect an estabilished parentage. That's working.
I also understand that even if i make a simple GU call for ORDER (before GNP for message)with no command code 'P', it will work out. |
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Sandy Zimmer
Active Member
Joined: 13 Jun 2007
Posts: 826
Location: Wilmington, DE
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Are you thinking that by setting parentage, that you are still positioned on the root segment - the order? Just remember that you are always positioned on your last successful call.
Are you using any SSA when retrieving your child segments? If you are not using an SSA when retrieving the child segments, you will most likely be checking for "GA" and "GK" - which indicates that you have made a sucessful call but you have retrieved that you have now retrieved a different segment type. Also, if parentage has not been set, GNP should not be executed - if it is, no segment will be retrieved and you will get a return status code "GP".
I like to control where I am by using the example I gave. I also like the most straight forward, easiest way to maintain and enhance the program. I cannot understand why not use the easiest method. I do not - at this time - understand why setting parentage is important? |
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Bitneuker
CICS Moderator
Joined: 07 Nov 2005
Posts: 1104
Location: The Netherlands at Hole 19
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| Multiple PCS's are costly. Command codes may help out like the V-code. Some searching and reading might help like here |
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