If you found your SQL Database performance is very slow then you can check below points.
1.Check if any blocking.
2- Check execution plan for any costly operator.
3- We can run DTA and take help from that but keep in mind it's not necessary to implement all suggestions provided by DTA.
4. Index fragmentation .
5. Missing indexes.
6. Stale update stats
7. Blocking & Deadlocks of queries.
8. Excessive compilation & recompilation.
9.Check long queries using trace of suspended records on high working time of transactions.
10.Check RAM utilization at SQL Server.
1.Check if any blocking.
2- Check execution plan for any costly operator.
3- We can run DTA and take help from that but keep in mind it's not necessary to implement all suggestions provided by DTA.
4. Index fragmentation .
5. Missing indexes.
6. Stale update stats
7. Blocking & Deadlocks of queries.
8. Excessive compilation & recompilation.
9.Check long queries using trace of suspended records on high working time of transactions.
10.Check RAM utilization at SQL Server.