Hi Pedro,

SLM only supports high availability using a 3-server configuration, also known as a license triad. For details, see the following KB doc:

https://knowledgebase.serena.com/InfoCenter/index?page=content&id=S129439

For this to work you would need a 3rd machine, and this machine cannot go down if one of the active/passive machine is not operational, given 2 of the 3 machines need to be up. It is typically easier to pick 3 always-on servers, unrelated to any active/passive HA configuration, where one of those machines is allowed to go down.

For a 2-server configuration your choices are:

• Split licenses between servers. Expensive if half of those licenses cannot be used because the machine is off during the passive phase. Doable if both machines remain operational, with clients pointing to both servers, each supporting 50% of the users. You would lose 50% capacity at the time of a failure, though.
• Do not install licenses on passive HA machine, and only put those in place during a failure. At that point you would rehost your license, making all of them available on the previously passive machine. No loss of capacity, but not a fully automatic fail-over.
• A combination of the previous two, where the 50% loss in capacity is solved post fail-over by rehosting the licenses assigned to the server that went offline to the then active server.

For future planning: the next PVCS VM release will use the AutoPass License Server (APLS), which does support 2-server High Availability using an external Postgres, Oracle, or MS SQL database.

Kind regards,

- Richard.

Hi Richard,

thank you for your help!

I think we will go for your suggested 3rd option

We would decide to have a "main_server" where around 80% of our licences would be granted and a "secondary_server" where we would place the remaining 20% 

In that case, how would we configure the PVCS clients? We would like to avoid the necessity to reconfigure clients (we have quite a lot of them, actually) if our "main_server" is down.

I've seen in the KB of license triad configuration that it is possible to add more than one server as license manager separting them by commas. 

    Port@Server1,Port@Server2,Port@Server3

Could we configure clients to consume licenses like this?

Port@main_server,Port@secondary_server

Thanks again for your help and kind regards!!

Hi Pedro,

The syntax is similar to the license triad, but it uses a different separator character. The comma (",") that is used for a triad indicates all servers are equal, so if server 1 responds "I don't have a license available" the client won't waste time trying to talk to servers 2 and 3, as they all provide the same answer. The client only tries to connect to servers 2 and 3 if server 1 goes offline.

In your setup, you want the client to talk to server 2 if server 1 has no licenses available. To do this, use a semi-colon (";") if the client runs on Windows, and a colon (":") if the client runs on Linux/UNIX. An easy way to remember is that this matches the PATH separator character of the OS where the PVCS client is running.

Please let me know if you have any follow-up questions.

With kind regards,

- Richard.