Lesson Learned #337: HADR_SYNC_COMMIT Wait Type Delay in Azure SQL Database
Introduction to HADR_SYNC_COMMIT Wait Type
High Availability and Disaster Recovery (HADR) is a set of features in Azure SQL Database that enables users to configure a database for high availability and disaster recovery. When a database is configured for HADR, the primary and secondary databases are kept in sync by the process of log shipping. Log shipping replicates transactions from the primary database to the secondary database. When the log shipping completes successfully, the HADR_SYNC_COMMIT wait type is used to wait for the secondary database to catch up with the primary database.
The HADR_SYNC_COMMIT wait type is a normal wait type that is encountered in an HADR environment. It is a sign that the secondary database is lagging behind the primary database. In certain cases, the wait time can become excessive and cause performance issues.
What Causes HADR_SYNC_COMMIT Wait Type Delay?
The HADR_SYNC_COMMIT wait type is encountered when the log shipping process is taking longer than expected. There are several possible causes for this. These include:
* Insufficient log shipping bandwidth: Log shipping requires a certain amount of bandwidth to complete the process. If the bandwidth is insufficient, the process will take longer.
* High transaction volume: If the transaction volume is high, the log shipping process will take longer.
* Corrupted log files: Corrupted log files can cause the log shipping process to take longer.
* Network latency: Network latency can cause the log shipping process to take longer.
* Inadequate hardware resources: Insufficient hardware resources can cause the log shipping process to take longer.
How to Troubleshoot HADR_SYNC_COMMIT Wait Type Delay?
The first step in troubleshooting HADR_SYNC_COMMIT wait type delay is to identify the cause of the delay. The cause can usually be identified by looking at the performance counters and system metrics. Once the cause has been identified, the appropriate action can be taken to resolve the issue. For example, if the cause is insufficient log shipping bandwidth, then more bandwidth can be allocated. If the cause is high transaction volume, then the transaction volume can be reduced. If the cause is corrupted log files, then the log files can be repaired. If the cause is network latency, then the network can be optimized. And if the cause is inadequate hardware resources, then more hardware resources can be allocated.
Conclusion
The HADR_SYNC_COMMIT wait type is a normal wait type that is encountered in an HADR environment. In certain cases, the wait time can become excessive and cause performance issues. The first step in troubleshooting HADR_SYNC_COMMIT wait type delay is to identify the cause of the delay. Once the cause has been identified, the appropriate action can be taken to resolve the issue. By understanding the causes of the HADR_SYNC_COMMIT wait type delay and taking corrective action, it is possible to reduce the impact on performance and ensure that the secondary database remains in sync with the primary database.
References:
Lesson Learned #337: HADR_SYNC_COMMIT wait type delay in Azure SQL Database
1. Azure SQL Database
2. Lesson Learned #337
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