SQL Server Always On Series - Step-by-Step Guide for Joining Replicas

SQL Server Always On Series - Step-by-Step Guide for Joining Replicas
Introduction
Welcome to the SQL Server Always On Series! In this video, we'll delve into the complexities of joining replicas in an Always On Availability Group. Joining replicas is a critical step in establishing a robust high-availability environment, but it comes with its share of challenges.

Understanding Error 1412 - The Main Challenge
What is Error 1412?
Error 1412 indicates that the remote copy of the database has not been rolled forward to a point in time that aligns with the local copy of the database log.

Why Does It Occur?
Explore the reasons behind Error 1412, including issues with log backups, log sequence numbers (LSN), and the restoration sequence.

Resolving Error 1412 - Step-by-Step Guide
Confirm Backup Sequence
Ensure a full database backup and subsequent log backups are taken on the primary replica. Verify the completeness of the backup sequence.

Checking Log Chain Integrity
Use the RESTORE HEADERONLY command to inspect log sequence numbers (LSN) in backup files. Learn how to identify and resolve log chain issues.

Restoring Full and Log Backups on Secondary
Demonstrate the process of restoring the full database backup and necessary log backups on the secondary replica to synchronize it with the primary.

Additional Errors and Their Resolutions
1) Failed to Join Database to Availability Group
Explore common reasons for the failure to join a database to an availability group, including network issues and permissions. Provide troubleshooting steps and solutions.

2) Exception While Executing T-SQL Statement
Investigate exceptions occurring during T-SQL execution. Check SQL Server error logs for details and guide viewers on resolving T-SQL-related errors.

4) Msg 4305, Msg 3013 - Backup and Restore Issues
Examine and resolve issues related to restoring backups. Clarify the importance of restoring the correct sequence of backups and handling specific error messages.

5) No Full Database Backup Selected
Address the scenario where no full database backup is selected for restoration. Guide users on selecting and restoring the necessary backups.

6, 7, 8) Database Already Exists on Secondary
Discuss the errors related to existing database files on the secondary replica. Demonstrate how to remove existing files and use the WITH REPLACE option during restoration.

General Tips and Best Practices
Check Disk Space
Highlight the importance of verifying sufficient disk space on both primary and secondary replicas before initiating any joining processes.

Review SQL Server Error Logs
Encourage viewers to regularly check SQL Server error logs for additional insights into errors and potential causes.

Conclusion
Congratulations! You've now navigated through the intricate process of troubleshooting replica joining issues in SQL Server Always On Availability Groups. Establishing a robust and error-free environment is crucial for maintaining high availability in your SQL Server infrastructure.

Failed to join the database 'ArCReactor' to the availability group 'JBSAG' on the availability replica 'JBSAG3'. (Microsoft.SqlServer.Management.HadrModel)

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

The remote copy of database "ArCReactor" has not been rolled forward to a point in time that is encompassed in the local copy of the database log. (Microsoft SQL Server, Error: 1412)

Msg 4305, Level 16, State 1, Line 1
The log in this backup set begins at LSN 875000022860000001, which is too recent to apply to the database. An earlier log backup that includes LSN 869000008377600001 can be restored.
Msg 3013, Level 16, State 1, Line 1
RESTORE LOG is terminating abnormally.

No full database backup is selected to be restored. (Microsoft.SqlServer.SmoExtended)

The databases ArCReactor already exist on secondary JBSAG3. (Microsoft.SqlServer.Management.HadrModel)

Checking for the database files on the secondary replica JBSAG3 resulted in an error. The following files already exist. F:\data\ArCReactor.mdf,F:\log\ArCReactor_log.ldf (Microsoft.SqlServer.Management.HadrModel)

Checking for the database files on the secondary replica JBSAG3 resulted in an error. The following files already exist. F:\data\ArCReactor.mdf,F:\log\ArCReactor_log.ldf (Microsoft.SqlServer.Management.HadrModel)

SELECT transferred_size_bytes/1024./1024./1024. transferred_size_GB,database_size_bytes/1024./1024./1024. database_size_GB,*
FROM sys.dm_hadr_physical_seeding_stats


DECLARE @LSN NUMERIC(25,0) = 869000008377600001;

SELECT
bs.database_name,
bs.backup_start_date,
bs.first_lsn,
bs.last_lsn,
bs.[type],
bmf.physical_device_name AS backup_filename
FROM
msdb.dbo.backupset bs
INNER JOIN
msdb.dbo.backupmediafamily bmf
ON
bs.media_set_id = bmf.media_set_id
WHERE
bs.first_lsn GT= @LSN
ORDER BY
bs.backup_start_date DESC;