Category: Performance Tuning

  • SQL Server Wait Types Library

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    Wait statistics are the single best first step in any SQL Server performance investigation. Every time a query waits on a resource, whether that’s a lock, disk I/O, a transaction log flush, a memory grant, or something else, SQL Server records it. By the time a performance problem appears, the evidence is usually already sitting…

    Written by

    Peter Whyte

  • How to Check Blocking SPIDs in SQL Server

    Blocking is one of the most common causes of performance issues in SQL Server. When one session holds a lock on a resource and another session needs that same resource, the second session waits. If that wait persists, users experience slowness. Understanding how to quickly identify blocking SPIDs is a core DBA skill. This guide…

    Written by

    Peter Whyte

  • Script: Identify Long-Running Queries

    This script returns currently executing queries ordered by elapsed time. It helps identify long-running requests that may be causing blocking, resource pressure, or user-facing delays. This is typically used during live performance incidents when users report slowness or when the instance appears busy. The Script Example Output The result set shows currently executing sessions ordered…

    Written by

    Peter Whyte

  • Script: Identify Missing Indexes

    This script returns the highest-impact missing index recommendations based on cumulative workload statistics. It helps identify tables where SQL Server believes additional indexes could significantly improve query performance. This is useful during performance tuning, workload reviews, and when investigating high read activity or inefficient query plans. The Script Example Output The result set shows the…

    Written by

    Peter Whyte

  • Script: Check Index Fragmentation Across All Databases

    This script checks index fragmentation levels across all online databases on the instance. It helps identify heavily fragmented indexes that may require maintenance. This is useful when reviewing index health, validating maintenance jobs, or troubleshooting performance issues related to inefficient index access. The Script Example Output The result set shows indexes across all user databases,…

    Written by

    Peter Whyte

  • Script: I/O Usage by Database

    This script returns total read and write activity per database based on file-level I/O statistics. It helps identify which databases are generating the most disk activity on the instance. This is commonly used during performance troubleshooting, storage pressure investigations, and workload analysis. The Script Example Output The result set shows one row per database, including…

    Written by

    Peter Whyte

  • Script: Top Wait Statistics

    This script returns the top wait types since the last SQL Server restart or wait statistics clear, excluding common idle and background waits. It provides a quick high-level view of where the instance is spending time. This is often the first script run during performance investigations to identify whether the primary pressure is related to…

    Written by

    Peter Whyte

  • Script: Check Worker Threads and Active Sessions

    This script shows the current SQL Server worker thread count along with all active sessions and requests. It provides a live view of CPU usage, blocking, waits, running commands, and transaction activity. This is a practical script for performance troubleshooting when an instance appears busy, unresponsive, or under pressure. The Script Example Output The first…

    Written by

    Peter Whyte

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