On Monday, 10/23/2017 at 12:38 GMT, Michael MacIsaac <[email protected]> 
wrote:
> The wrapper function tries to trap the error for buffer overflow and if
> found, resend the vmcp command with the required size.  So I'm guessing 
the
> vast majority of vmcp calls made will have output that will fit in 32K.
>
> Does this look like a good approach?

You only want to reissue QUERY/INDICATE-type commands.  IMO, it's best to 
assess the type of command before issuing it.  If you have device-related 
commands (e.g. VARY rdev and VARY PATH) with large ranges, you will want 
to split the command into multiple commands with smaller ranges and then 
combine the output.  If you don't do that, you are going to get failures 
on the 2nd issuance of the command.

E.g. 
VARY OFF PATH 8 FROM EC67-EC68
00: Vary path 08 offline command initiated 
00: Vary path 08 offline command complete 
Ready; T=0.01/0.01 10:24:31

VARY OFF PATH 8 FROM EC67-EC68 
00: Vary path 08 offline command initiated 
00: Path 08 is already offline for device EC67
00: Path 08 is already offline for device EC68 
00: Vary path 08 offline command complete

And note that getting the errors will significantly increase buffer usage.

Alan Altmark

Senior Managing z/VM and Linux Consultant
IBM Systems Lab Services
IBM Z Delivery Practice
ibm.com/systems/services/labservices
office: 607.429.3323
mobile; 607.321.7556
[email protected]
IBM Endicott

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