I've an update for those of You who may concern:
placing the two Parameter/values
<add key="SnapmirrorRetry" value="10" />
<add key="SnapmirrorTimeout" value="500" />
into the SnapCenter configuration file (as matte mentioned did not solve the issue -in total-, as I had no clue how to find proper values.
I opened a support-call and got the advise to only set the first parameter/value to
<add key="SnapmirrorRetry" value="90" />
and from that time on, snapvault copy processes completed more often in-time and got reported towards the
SnapCenter repository.
I tested in three steps:
1st: I changed the scheduling.
During the vault-Situation, four HANA ressources belonging to a common svm and it's coresponding snapvault svm were scheduled for snap at 8:pm
I separated them by 15 minutes
result: only sometimes one schedule finished with the mentioned warning.
2nd: I put the snapmirrorretry parameter with value 90 in place
result: All schedules went fine.
3rd: I rescheduled all four jobs to start simultaniously again
All four schedules started at 8 pm
result: All schedules went fine.
Even though this situation might be cleared there is still one thing left: Whenever communication between NetApp and Snapcenter either stucks (reaches a timeout) or interrupted,
there seems to be no way getting SnapCenter Repository in sync again with Netapp's (snapshot/snapvaoul/snapmiror) facts.
My Support Call is still open and I wonder if this is stuff for an RFC. I'll keep You updated.