Understanding Query Wait Types

What It Is

Query wait types tell you what SQL Server is waiting on when executing a query. These indicators help DBAs pinpoint performance bottlenecks beyond just slow-running SQL.

Why It Matters

Wait types help you to see delays associated with different underlying workload activities.  For example a CX Packet wait indicates that we are waiting on CPU resources. “Lock_M_IS” would indicate a blocking condition. Backup activity may be “Backup Buffer”, “Backup IO” “pageIO Latch” or “Write log” activity. all indicating a slowdown based on certain wait types or waiting for resources.

How to Spot It

• Run sys.dm_os_wait_stats to view server-wide wait types.
• Look for high counts/durations in waits like PAGEIOLATCH, CXPACKET, or LCK_M_X.
• Use SQL Diagnostic Manager to visualize real-time wait stats.

How to Fix or Address It

• Address storage issues (e.g., slow disks = high PAGEIOLATCH).
• Optimize parallelism settings if CXPACKET is high.
• Resolve locking/blocking patterns for lock-related waits.

Key Takeaway

Understanding wait types helps DBAs go from guessing to diagnosing SQL Server slowdowns.

How Can Idera Help?

SQL Diagnostic Manager can help you quickly identify top waits and related queries.  For more information on SQL Diagnostic Manager or to start a free trial, visit us HERE.