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XML Parse and restartability

 
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misi01
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Location: Stockholm, Sweden

PostPosted: Wed Dec 02, 2015 6:46 am    Post subject: XML Parse and restartability Reply with quote

We obviously have generalized programs in place in order to be able to restart a BMP halfway through its processing. This involves calling the general program to take checkpoints regularly (mainly to release locks on DB2 tables).

Using GSAM, we can be assured that IMS will position any read pointers to the relevant rows in any files. This works fine using "ordinary" files. Now, to the crunch. In the example that's causing a problem, we're reading an XML file. Let's assume it looks something like this:-

Code:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Skatteverket
xmlns="http://xmls.skatteverket.se/se/skatteverket/ai/instans/infoForBeskattning/1.2"
xmlns:gm="http://xmls.skatteverket.se/se/skatteverket/ai/gemensamt/infoForBeskattning/1.2"
xmlns:ku="http://xmls.skatteverket.se/se/skatteverket/ai/komponent/infoForBeskattning/1.2"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" omrade=""
xsi:schemaLocation="http://xmls.skatteverket.se/se/skatteverket/ai/instans/infoForBeskattning/1.2
http://xmlsutv.skatteverket.se/schemalager/se/skatteverket/ai/kontrolluppgift/instans/Kontrolluppgifter_1.2.xsd">

<ku:Avsandare>
   various records here
</ku:Avsandare>

<ku:Blankettgemensamt>
  various records here
</ku:Blankettgemensamt>


and now come the actual documents
Code:

<ku:Blankett nummer="2322">
   various records
</ku:Blankett>
<ku:Blankett nummer="2322">
   various records
</ku:Blankett>                            <------ checkpoint taken here
<ku:Blankett nummer="2322">         <------- Document nr 3
   various records
</ku:Blankett>
 
etc etc


Let's assume the program crashed after the checkpoint was taken above. When we restart the program, the first record read will be the Document nr 3 (as expected).

Trouble is, according to our DBA, the XML Parser won't work properly since it's missing the "starting records" in the XML string. (this according to the DBA)

Has anyone experienced this sort of behaviour? Is there any way round it other than simply reading the file from the very beginning ?
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kolusu
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PostPosted: Wed Dec 02, 2015 10:10 am    Post subject: Re: XML Parse and restartability Reply with quote

misi01 wrote:

Let's assume the program crashed after the checkpoint was taken above. When we restart the program, the first record read will be the Document nr 3 (as expected).

Trouble is, according to our DBA, the XML Parser won't work properly since it's missing the "starting records" in the XML string. (this according to the DBA)

Has anyone experienced this sort of behaviour? Is there any way round it other than simply reading the file from the very beginning ?


Misi01,

Unless I am missing something obvious, why can't you simply save the first 3 lines in the Checkpoint area and upon restart read those values once again and start off where you crashed.
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kolusu
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PostPosted: Wed Dec 02, 2015 10:33 am    Post subject: Reply with quote

misi01,

Update : I just ran the example of xml parse listed below without the header line (basically mimicking restart feature) the and it worked fine.

http://www-01.ibm.com/support/knowledgecenter/SS6SG3_4.1.0/com.ibm.entcobol.doc_4.1/PGandLR/ref/rpxml21e.htm


I am using Enterprise COBOL version 5.2
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William Collins
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PostPosted: Thu Dec 03, 2015 2:16 am    Post subject: Reply with quote

Since XML can be presented to you as one big lump or one element at a time or something in between, the PARSE allows processing for that. You never have to build a complete XML document before you are able to PARSE it.
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misi01
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PostPosted: Sat Dec 05, 2015 4:17 am    Post subject: Reply with quote

Thanks to both.I'll have to keep testing and see what happens.

Kolusu - your idea of removing the headers and running it as a simple QSAM input file is a good idea.I'll see what it produces and get back
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misi01
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PostPosted: Thu Jul 07, 2016 4:23 am    Post subject: Thought I'd append an update to my original question Reply with quote

Kolusu - you were correct. I'll append an example and the code I used to be able to restart using GSAM as an input file. First of all, the file's root element

Quote:

<?xml version="1.0" encoding="utf-8"?>
<ns1:InstrumentInfo xmlns:ns0="xxx.xxx.Types.v1" xmlns:ns1="xxx.xx.Instrument
<ns1:TargetSystem>INETExt</ns1:TargetSystem>
<ns1:FileTimestamp>2015-10-16T11:17:13</ns1:FileTimestamp>
<ns1:NoOfInstruments>13738</ns1:NoOfInstruments>
<ns1:InstrumentDataList>


Then each element starts with the following:-
Quote:

<ns1:InstrumentData>
<ns1:VpdbId>2</ns1:VpdbId>
<ns1:InstrumentIdentificationList>
<ns0:InstrumentIdentification xsi:type="ns0:InstrumentId
<ns0:InstrumentIdType>VPDB Id</ns0:InstrumentIdType>
Etc etc


My code to read the GSAM file contains the following:-
Code:

             if vx-start-of-document-read-no                 
               perform xma-append-start-of-document         
             end-if                                         

And
Code:

      *****************************************************************
      * Append all the records "belonging" to the start-of-document   
      * to aa-start-of-document                                       
      *****************************************************************
       xma-append-start-of-document section.                           
      *                                                               
           move aa-shbg0910-post-lgd   to ix-1                         
           compute ix-2                = ix-1                         
                                       + ix-start-of-document         
      *                                                               
           evaluate true                                               
             when ix-2 > length of aa-start-of-document 
      *        The length of aa-start-of-document is too small
      *        to receive the complete root element. Tell them
      *        and abend                                                   
               move kk-al-01           to shbgg015-avbrottslage       
               move kk-er              to shbgg015-returkod           
               string                                                 
                 'aa-start-of-document is defined with too few '         
                 'characters to receive ALL of the START-OF-DOCUMENT. '     
                 'Increase (if possible) and try again'                 
                                          delimited by size           
                 into shbgg015-meddelande-tab                         
               end-string   
               perform xf-user-snap   
               perform xg-abend                                                 
             when other                                               
               string                                                 
                 aa-shbg0910-post-vardata(1:ix-1)                     
                                          delimited by size           
                 into aa-start-of-document                             
                 with pointer ix-start-of-document                     
               end-string     
           end-evaluate       
      *                       
           exit.   


At the start of the program, we call a module to check whether we’re running “normally”
or restarting after an abend
Code:

           if vanlig-korning                                   
      *      Normal scenario             move 1                    to ix-start-of-document         
             perform xm-las-gsam-n022201                               
           else                                                       
      *      Restart                                                 
             move ' '                  to aa-shbg0910-post-vardata     
      *      Pretend we read all the starting records and catenated   
      *      then into ONE record                                     
             move aa-start-of-document to aa-shbg0910-post-vardata     
             move ix-start-of-document to aa-shbg0910-post-lgd         
           end-if                                                     


And finally, the actual XML PARSE
Code:

           xml                                                       
             parse aa-shbg0910-post-vardata(1:aa-shbg0910-post-lgd) 
               processing procedure cb-xml-handler                   
             on exception                                           
               perform ca-hantera-parse-exception                   
           end-xml                                                   


Have to append this as-is, since there're obviously some UTF characters somewhere in it so I can't preview it.
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