Wait Type HADR_DBSEEDING_LIST

Wait statistics, in the context of SQL Server, refer to the amount of time that a query spends waiting to access data in the database. When a client application requests data from the database, the request is placed in a queue and the client application must wait for its turn to access the data. The time that the query spends waiting is called a "wait" and is tracked by SQL Server. This information can be used to identify potential performance bottlenecks and optimize the performance of the database. Wait statistics are commonly used by database administrators to diagnose and troubleshoot performance issues in SQL Server.

In SQL Server, wait types help us understand where processes may be experiencing delays. One specific wait type, HADR_DBSEEDING_LIST, is related to high availability and disaster recovery (HADR) configurations, specifically with the seeding process in Always On Availability Groups. When this wait type appears, it typically means SQL Server is in the process of initializing or synchronizing a database with its replica. In this post, we’ll explore what HADR_DBSEEDING_LIST means, when it appears, and how it might impact SQL Server performance.

What Is the HADR_DBSEEDING_LIST Wait Type?

The HADR_DBSEEDING_LIST wait type appears when SQL Server is waiting during the seeding of a database in an Always On Availability Group. Seeding is the process of copying a database from the primary replica to a secondary replica so they are synchronized. This ensures that the secondary replica has the same data as the primary and can take over if needed.

When SQL Server is seeding a database, it might have to wait for several reasons, such as network delays, disk performance, or the amount of data being transferred. The HADR_DBSEEDING_LIST wait type simply means SQL Server is currently waiting during this transfer process.

When Does HADR_DBSEEDING_LIST Appear?

You’ll typically see the HADR_DBSEEDING_LIST wait type in Always On Availability Group environments, particularly when a new secondary replica is being initialized or when a full database copy is required for synchronization. Common scenarios include:

• Adding a New Replica – When a new secondary replica is added to an Availability Group, SQL Server must seed the database to that replica, which can result in HADR_DBSEEDING_LIST waits.
• Resynchronizing a Secondary Replica – If a secondary replica falls behind or loses synchronization, SQL Server may need to reseed the database, leading to these waits.
• Large Database Synchronizations – For larger databases, the seeding process can take longer, resulting in more noticeable HADR_DBSEEDING_LIST waits.

These waits are normal during seeding operations, as SQL Server ensures that the primary and secondary databases are fully synchronized for high availability.

Why HADR_DBSEEDING_LIST Waits Matter

While HADR_DBSEEDING_LIST waits are expected during the initial synchronization process, they can impact performance and data availability, especially in environments with large databases or slow networks. High or prolonged HADR_DBSEEDING_LIST waits may signal:

• Network Bandwidth Limitations – If the network between the primary and secondary servers has limited bandwidth, it can slow down the seeding process.
• Disk Performance Constraints – Slow disk performance on either the primary or secondary server can delay data transfer and increase wait times.
• Large Volume of Data – Larger databases naturally take longer to seed, especially if there’s a high volume of data changes during synchronization.

How to Address HADR_DBSEEDING_LIST Waits

If you are seeing high HADR_DBSEEDING_LIST waits, here are some strategies to help speed up the seeding process and reduce wait times:

• Optimize Network Bandwidth – Ensuring sufficient network bandwidth between primary and secondary replicas can help reduce delays. Using a dedicated network for HADR traffic can improve performance.
• Use Faster Storage – Consider upgrading storage to faster drives (such as SSDs) for both the primary and secondary replicas to allow quicker data transfer.
• Schedule Seeding During Off-Peak Hours – Performing initial seeding or reseeding during times of low database activity can reduce the impact on system performance.
• Monitor and Reduce Database Size – Reducing the database size, if feasible, can speed up the seeding process, especially if you can archive old data or use partitioning.

Conclusion

The HADR_DBSEEDING_LIST wait type in SQL Server appears when the system is waiting during the seeding process in an Always On Availability Group. While these waits are normal during synchronization, frequent or prolonged waits can indicate network or disk performance issues, especially with larger databases. By optimizing network and storage resources, scheduling seeding during off-peak times, and monitoring database size, you can help reduce HADR_DBSEEDING_LIST waits and improve SQL Server’s high-availability performance.

If you need help with SQL Server high availability, performance tuning, or managing Always On Availability Groups, Stedman Solutions offers managed services to ensure your SQL Server environment runs efficiently and reliably.

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Applies to

Related Waits

See Also

• More About HADR_DBSEEDING_LIST