Hi,
Regarding your question, I've made a test in SAP HANA SPS07 rev. 70 early this year. You can take it as a reference.
In my test environment, there were three hosts, one master, one slave and one standby as follows.
I created a very simple partitioned table named "STUDENT".
After the insertion, when you opened the definition of the table and switched to the "Runtime Information", you could find there were 2 records on the master and 1 record on the slave. There was no record on the standby.
At this time, when you made a select, everything was fine. You could see three records.
Then I stopped the slave.
At this time, I ran the select statement but failed. This is because there was one record on the slave and the slave was stopped (the standby was not started yet). So you get everything or you get nothing. In this case, you got nothing.
After the standby was started and took over the data which was on the slave, I could succeed to run the SQL again.
In short, if you use host-level HA which means you have only one SAP HANA system and there is(are) standby host(s) in your SAP HANA system, "seamless" is impossible. This is because of the "shared nothing" concept in SAP HANA distributed system.
Best regards,
Wenjun