Skype for Business - Why Can't I Escalate to a Conference?

I had a customer a few weeks ago that could not escalate to a conference. They were having a P2P call with someone, tried to add a third user to the conversation and received an error each time. The problem had been going on for about a week and they asked if I could take a look and see what was going on.

I'll admit, I've heard of this issue before, but I had not seen it yet. I started parsing the Lync Event Log on the FE server and noticed a lot of the following SQL Errors:

The 'General' tab included more data, but here is the most pertinent thing we need to focus on:

The transaction log for database 'rtcxds' is full due to 'LOG_BACKUP'.

I'm not a SQL expert, but shouldn't there be a way to increase or decrease the size of the logs? Well, there is, but it turned out to be more convuluted than I had hoped.

I logged onto the BE SQL server where the rtcxds database is located. I right clicked on the database, went to 'Properties' -> 'Files' and then clicked on the '...' button for the log file. Since there was plenty of space on the disk, I tried to increase the size of the log file from 10 GB. I received the following error:

SQL Server Error 9002: Transaction Log is Full

Yeah, understood. That's why I'm trying to increase the size, so work with me here, ok? 😉

After some Googling, I found that I have to take a backup before increasing the size. However, after talking with the customer, they're taking pretty frequent backups already. So, is there a way to take a back without really taking a backup? Yes, of course!
backup log
dname TO DISK = 'NUL:'; (note: just one 'L' is correct)

Entering the above two lines into a sql query (sans my note: on line two) within SQL Server Managment Studio tells SQL to write a backup to 'Null'. As far as SQL is concerned, a write happened, so we're all good.

After running the query above I was able to increase the size of the log file location and the customer confirmed they could escalate to a conference again. I checked the Lync Event Logs on the FE server and noticed the following message: