pvput with Sub-structures

[Dennis Neidherr via Tech-talk <tech-talk at aps.anl.gov>]

Dear all,

Happy new year!
At the moment I am playing with pvAccess (and p4p) to see how this is 
working.
So for my tests, I have successfully built the pvxs-support-module and 
created an application which uses it.
In the db File I added two new records:
record(ai,"myTest1")
{
    field(SCAN, "Passive")
    field(VAL, 2)
}
record(ai,"myTest2")
{
    field(SCAN, "Passive")
    field(VAL, 4)
}

And I added a json-File, which is loaded at the startup of the IOC:
{
    "grp:name": {
        "X": {"+channel":"myTest1.VAL"},
        "Y": {"+channel":"myTest2.VAL"}
    }
}

pvget and pvmonitor seem to work, but my question is now: What is the 
correct command to be used with pvput?
First, I tried (very naive):
pvput grp:name 4 5
This is obviously not working. Then I checked the help of the 
pvput-command and there is written:
...
Sub-structure(s)
  pvput group:pv some='{"value":1.234}' other='{"value":"a string"}'
...

So I tried it:
pvput grp:name X='{"value":"77"}'
This is also not working (The error is just "No fields changed").

From my internet search I got this link:
https://urldefense.us/v3/__https://mrkraimer.github.io/website/developerGuide/pvTools/pvTools.html__;!!G_uCfscf7eWS!buHkU2vY2nC-8z2UrnhpcT58Z50NjPTQVfA3ka4Pe3TQwIPKPUKS3b-mB8S1-9ocmlLnmM0j4F50C1K5Vi01tz0d$ 

So I tried also:
pvput -r "X" grp:name X='{"value":"77"}'

But again the same "error" is shown.

I also tried it in python (p4p library):
...
        v = await ctx.get("grp:name")
        print("Old value: " + str(v.X.value))
        v.X.value = 42
        await ctx.put("grp:name", v)
        u = await ctx.get("grp:name")
        print("New value: " + str(u.X.value))
...
But again: The value is not set and the error is "No fields changed".
Since this error is a bit unspecific, I have no ideas how to proceed.

Thanks in advance for any help,
Greetings Dennis

--
Dr. Dennis Neidherr
Department: Electronics (EEL)

Phone: +49-6159-71-1885
Email: d.neidherr at gsi.de

GSI Helmholtzzentrum für Schwerionenforschung GmbH
Planckstraße 1, 64291 Darmstadt, Germany, https://urldefense.us/v3/__http://www.gsi.de__;!!G_uCfscf7eWS!buHkU2vY2nC-8z2UrnhpcT58Z50NjPTQVfA3ka4Pe3TQwIPKPUKS3b-mB8S1-9ocmlLnmM0j4F50C1K5Vv2QPngT$ 

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