This is possible but with some caveats. If you are using the BYOL licensing system and have an existing license key active on your Access Server, it is not possible to change the licensed amount on the existing license key. But what you can do is purchase an additional license key and activate it on the same Access Server. The licensing system will then simply add them up. For example, if you have a license key that unlocks 10 connections installed on your Access Server and find that you need 30 in total, you can purchase a license key for 20 connections and activate it on that same Access Server. The license key for 10 connections and the license key for 20 connections then are both active and are added up to a total of 30 connections. The caveat here is that the license start date and end date of the newly purchased license key will be different for these two license keys. However when you renew license keys on our website you do have the option to select both license keys and set a single future date for both of them. The renewal system calculates and adjusts the costs automatically in such a case.
If you are using the Amazon AWS tiered instances licensing system then things are unfortunately not quite so easy, but still possible. Due to the way the licensing system works on Amazon AWS, the instance properties are very firmly tied to the amount of licensed connections. At this time you cannot click a button to switch from a 10 connected devices instance to a 25 connected devices instance. The solution here is to make a backup of the your existing AWS instance's OpenVPN Access Server configuration databases, and bring up a new instance with the desired amount of connected devices, and restore the backup of the configuration to that system. There are some caveats. If the old system was configured to function on IP basis instead of an FQDN DNS address, then clients that were installed on the old Access Server instance will continue to attempt to reach the old IP address. If possible, move the IP address to the new instance so that clients can find the server again. But the best option is always to set up an FQDN DNS address, which we recommend for any Access Server installation. With that, you can simply update the DNS record to point it to the IP address of the new instance, and clients will then automatically find the correct instance. And finally of course, the old instance should be stopped to avoid continuing to incur costs on the old instance.
We have a migration guide that will help you to move the existing server configuration from one installation of Access Server, to another. With the configuration of the Access Server moved in this manner, the clients will not need to be reinstalled or adjusted, they will just be able to connect to the new server installation automatically.