Background
Error code 45168 occurs when an Azure SQL Database experiences issues with geo-replication, a feature that enables the creation of secondary database replicas in different regions for high availability and disaster recovery. This error typically arises when there are connectivity issues, configuration mismatches, or limitations in the primary or secondary database that prevent the replication process from proceeding correctly.
Summary Table
Aspect | Details |
---|---|
Error Code | 45168 |
Error Message | Geo-replication could not be completed due to an issue with the primary or secondary database. |
Background | The database cannot establish or maintain a replication link between primary and secondary databases. |
Common Causes | 1. Network connectivity issues 2. Insufficient resources 3. Service tier mismatches 4. Database locking or high workload |
Workarounds | 1. Use backups as an alternative for disaster recovery 2. Set up a secondary in a different region |
Solutions | 1. Ensure stable network connectivity 2. Verify service tier compatibility 3. Restart geo-replication 4. Monitor replication health |
Example Check | SELECT qs.total_worker_time, q.text FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) q ORDER BY qs.total_worker_time DESC; |
Error Explanation
The error message for error 45168 typically reads:
Error 45168: Geo-replication could not be completed due to an issue with the primary or secondary database.
This error indicates that the SQL Database cannot establish or maintain the geo-replication link between the primary and secondary databases, preventing data from syncing across regions.
Common Causes
- Network Connectivity Issues: Network interruptions between the primary and secondary databases can disrupt the replication process.
- Insufficient Resources: The secondary database may lack resources such as DTUs or vCores to handle the replication workload.
- Configuration Mismatches: The primary and secondary databases must be configured in compatible service tiers and performance levels.
- Database Limitations: Certain features or settings, like incompatible indexes or certain types of data, may not support geo-replication.
- Database Locking or Blocking: High workload on the primary database can cause delays in data being replicated to the secondary.
Steps to Troubleshoot and Resolve Error Code 45168
1. Check Network Connectivity Between Primary and Secondary Regions
Geo-replication relies on a stable network connection between the primary and secondary databases. Network issues, such as high latency, packet loss, or regional outages, can disrupt the replication link.
Steps to Check Network Status:
- Go to the Azure Portal.
- Navigate to Azure Service Health.
- Check for any ongoing issues or outages in the regions where your primary and secondary databases are located.
If there is a network or regional issue, you may need to wait until the issue is resolved, as Azure will automatically attempt to re-establish the replication link once connectivity is restored.
2. Ensure the Secondary Database Has Sufficient Resources
Geo-replication requires that the secondary database has enough resources to handle the data being synced from the primary database. The secondary must be in the same or a higher service tier than the primary.
Steps to Check and Increase Secondary Database Resources:
- Go to Azure Portal.
- Navigate to the Secondary Database under your SQL Server.
- Under Settings, select Configure.
- Ensure that the service tier and DTUs or vCores match or exceed the configuration of the primary database.
- Increase the resources if necessary and apply the changes.
For example, if your primary database is in the Standard S2 tier, ensure the secondary database is also in Standard S2 or higher.
3. Verify Service Tier Compatibility Between Primary and Secondary Databases
The primary and secondary databases must be in compatible service tiers. For instance, if the primary database is in the Premium tier, the secondary should also be in Premium. Mismatches in service tiers can prevent replication.
Steps to Verify Service Tier Compatibility:
- Go to Azure Portal.
- Check the service tiers of both the primary and secondary databases.
- If they are mismatched, reconfigure the secondary database to match the primary’s service tier.
Example Compatibility:
- Primary: Standard S3
- Secondary: Standard S3 (or higher)
If the primary database is in Premium P2, ensure the secondary is also in Premium P2 or a higher tier.
4. Review Database Workload on Primary Database
A high workload on the primary database can cause delays or blocking issues that prevent data from syncing with the secondary. High transaction volumes, frequent inserts, or heavy queries can slow down the replication process.
Steps to Reduce Workload on Primary Database
- Use Query Performance Insights in Azure Portal to identify heavy or long-running queries.
- Optimize queries by adding indexes or simplifying complex operations.
- Consider scaling up the primary database to handle the workload more effectively, which may reduce replication delays.
Example Query to Identify Heavy Queries:
SELECT TOP 10
qs.total_worker_time AS CPU_Time,
qs.total_elapsed_time AS TotalTime,
q.text AS QueryText
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) q
ORDER BY qs.total_worker_time DESC;
5. Restart Geo-Replication
If the issue persists, try restarting the geo-replication link. Restarting can reinitialize the connection and may resolve transient issues.
Steps to Restart Geo-Replication:
- Go to Azure Portal.
- Navigate to your Primary Database.
- Under Settings, select Geo-Replication.
- Click on the secondary database and choose Remove Replication to remove the existing replication link.
- After removing the link, reconfigure geo-replication by adding the secondary database back.
Note:
This step will cause temporary downtime for replication, so plan accordingly if it impacts your disaster recovery strategy.
6. Monitor Geo-Replication Health
Azure provides geo-replication health status that you can monitor to get real-time insights into the status of the replication link and any potential issues.
Steps to Monitor Geo-Replication Health:
- Go to Azure Portal.
- Navigate to your Primary Database.
- Under Settings, select Geo-Replication.
- Review the replication health status and look for indicators of connectivity issues or delays.
Azure SQL Database will attempt to recover from transient issues automatically, so regular monitoring can help identify patterns or recurring issues that may need further investigation.
Workarounds
- Manual Backups: If geo-replication cannot be established, consider using automated backups as an alternative for disaster recovery.
- Alternative Region Setup: If connectivity issues persist, consider setting up a secondary in a different region.
Solutions
- Check and Resolve Network Connectivity: Ensure stable network connectivity between primary and secondary regions.
- Ensure Resource Parity: Make sure the secondary database has enough resources and is in a compatible service tier.
- Reduce Workload on Primary Database: Optimize heavy queries or scale up the primary to reduce blocking and ensure smooth replication.
- Restart Geo-Replication: Restarting the replication link can clear transient issues and reinitialize the connection.
- Monitor Replication Health: Use Azure monitoring tools to keep track of geo-replication health and address issues proactively.
Example Scenario
Suppose you are using geo-replication to keep a secondary database in a different region as a disaster recovery option. You notice that replication has failed with the following error:
vbnetCopy codeError 45168: Geo-replication could not be completed due to an issue with the primary or secondary database.
Step 1: You check Azure Service Health and find no ongoing regional network issues.
Step 2: You go to the secondary database and check its resources, finding that it is in a lower tier than the primary. You upgrade the secondary database to the same service tier as the primary.
Step 3: You use Query Performance Insights to identify and optimize a few heavy queries on the primary database to reduce its workload.
Step 4: You restart geo-replication by removing and re-adding the secondary database to resolve the issue.
Step 5: You monitor the geo-replication health status in the Azure Portal to confirm that the replication link is now stable.