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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability Is It a Problem? No. The secondary replica redo model write-up lists it among the waits without performance impact, and Get Wait Statistics filters it out by default. What It Means Microsoft lists PARALLEL_REDO_WORKER_SYNC as…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability Is It a Problem? No. The secondary replica redo model write-up calls it an idle wait that is expected to occur regularly, and Get Wait Statistics filters it out by default. Every database on a…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? No. It is not a known contention point; our SQL Server 2025 lab had 82 waits totalling a quarter of a second. Get Wait Statistics does not filter it out,…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: ASYNC_NETWORK_IO Wait TypeRelated pillar: Performance & Troubleshooting Are They a Problem? They are the time spent inside external providers. Small amounts come with any linked server use. When the family becomes prominent, sessions are spending real time in provider code, and…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting ⚡The PREEMPTIVE_DTC_* waits are SQL Server waiting on the Distributed Transaction Coordinator (MSDTC) to begin, enlist in, commit or abort a distributed transaction. The time is spent in MSDTC and on the network between…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability ⚡PREEMPTIVE_HADR_LEASE_MECHANISM belongs to the Availability Group lease, the health check between SQL Server and the cluster. It is documented only as lease manager scheduling for support diagnostics, but in practice it ties to renewing the…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: ASYNC_NETWORK_IO Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? Usually not. It is not reported as a contention point, and it trails well behind OLEDB on linked server workloads; it was zero on our SQL Server 2025 lab. Get…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting ⚡These waits are SQL Server asking Windows, and usually a domain controller, which groups an account belongs to. At background levels they are normal. When they climb, either something is asking far too often…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting ⚡PREEMPTIVE_OS_AUTHENTICATIONOPS is SQL Server waiting on Windows for authentication work, which for domain accounts usually means a domain controller. Its average time per call is a latency meter for your authentication infrastructure. When it…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: Performance & Troubleshooting Two preemptive waits track Windows Server Failover Clustering calls, and this page covers both: PREEMPTIVE_OS_CLUSTEROPS: documented as internal use only; it is the generic wait for Windows failover cluster functions. PREEMPTIVE_CLUSAPI_CLUSTERRESOURCECONTROL: the SQLOS scheduler…

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