High CXPACKET / CXSYNC_PORT Waits in SQL Server
Troubleshooting
Problem
Cause
CXSYNC_PORT is a more granular wait type introduced in Azure SQL Database and SQL Server 2022; in earlier versions, it is included under CXPACKET. Both wait types indicate that SQL Server is spending time coordinating parallel query execution.
These waits are common and not necessarily problematic. However, they become a concern when the wait time for a query is disproportionately high compared to its CPU time, suggesting that the query spent excessive time waiting for parallel worker threads.
This behavior is typically associated with insufficient CPU resources or queries using high degrees of parallelism. Interpreting these waits can be tricky, as reducing parallelism may lower wait times but does not always improve overall query performance.
Solution
Recommended actions:
- Identify queries from concurrent workloads (including SEI) that use a high degree of parallelism. Review their execution plans and consider reducing parallelism where appropriate, keeping in mind that this may impact performance.
- Ensure that statistics and indexes on tables involved in high‑wait queries are up to date and optimized. Improving query efficiency reduces overall load on the SQL Server instance.