Yesterday morning I tried to login to SCVMM 2012R2 and I got below error. I logged it to MSSQL server over SQL Management studio to check out if availability groups are fine. After around 10 minutes of investigation I found out LOG partition on SQL server run out of free space. I had to extend LOG virtual disk drive, extend LOG partition on MSSQL server and restart SCVMM services to make it working again.
Database operation failed. Ensure that the SQL Server is running and configured correctly, and try the operation again. ID: 2604
If you are wondering how to extend virtual disk on Hyper-V 2012 R2 click on this link