Re: using DTAQ in COBOL

["Simon COulter" <shc@xxxxxxxxxxxxxxxxx>]


Hello Mary,

You wrote:
>We want the web program to send the data to a data queue and a COBOL program
>to process the record and then wait for the next one. What makes the COBOL
>program set on the READ statement and how do you handle opening and closing
>of files?

You don't READ from the data queue.  You call the QRCVDTAQ API.  You would 
submit the 
COBOL program as a batch process that opens its files and then waits for data 
on the 
queue.  The API supports a wait-time parameter that lets you decide to wait 
forever, 
wait for a finite period, or not wait at all.

>We want to halt the COBOL program and let the queue just build up while we
>run a backup on the files. Do you abort the job and let it close the files?
>Appreciate any advice.  

Be a little careful with this.  On RISC systems, the queue is sorted (if keyed) 
on the 
receive so if many entries arrive during the backup the COBOL program may 
appear to 
stall when you restart it after the backup -- it will catch up eventually.  
Also queues 
grow when the entries arrive faster than they are removed so you may have space 
considerations.

It would be nicer if you designed a communications method where the COBOL 
program can 
shut down when it gets a particular queue entry.  You could make the queue 
keyed and use 
a numeric priority as the key value.  Normal entries would be sent with a PTY 
of 5, 
END_NOW entries would be sent with a PTY of 0, END_AFTER_PROCESSING would be 
sent with a 
PTY of 9,  etc.  You might want to send a SUSPEND entry which causes the 
program to 
close the files and wait for a RESUME entry on the queue.

You might also want to consider designing a though-put monitor into the program 
so it 
can determine if the entries are arriving faster than it can handle and then it 
can 
submit a new copy of itself.  Once it has caught up extra copies could simply 
shut down.

You are limited only by your imagination and coding ability.

Regards,
Simon Coulter.

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