If your DualShield system consists of multiple DualShield servers in a high availability cluster, then you must follow the process below to upgrade the system.
Typically, you would have two DualShield servers set up as a MySQL Dual-Master or MS-SQL Merge-Replication cluster. For the description purpose, let us call them Master/Publisher and Slave/Subscriber.
Step 1: Check all SQL servers in the cluster, make sure they are in sync. See:
- How to check the status of a MySQL Dual-Master cluster
- How to check the status of a MS-SQL Merge-Replication cluster
Step 2: Upgrade the Master/Publisher server first (VERY IMPORTANT for MS-SQL Merge Replication. Do NOT upgrade the Subscriber/Slave server first)
Step 3: Wait for the Master/Publisher server to complete the upgrade process. See:
How to check if a DualShield server is fully started.
Step 4: Check both the Master/Publisher and Slave/Subscriber SQL server in the cluster again, make sure that they are in sync.
Step 5: Upgrade the Slave/Subscriber server