Not able to start SQL Server Services, what may be the reasons and how will you troubleshoot?

There are some basic reason if you not able to start the SQl Server Service:

1)     Master db files are not found on their location or corrupted

2)     Instance specific binaries or related binaries are either corrupted or disk is not available.

3)     Registry may be corrupt;

4)     Permissions may be messed up

5)     Antivirus may block the services to start

6)     Memory is not sufficient on server to allocate to SQL Server that time.

You can Troubleshoot the issue using following way:

1)     Check the SQL Server error log if created in instance root directory in Log folder

2)     Application and System logs in event viewer log

3)     Check resource (Memory and CPU) utilization on server that time.

4)     Check if relevant disks where SQL Server binaries located are attached/accessible from server