Hi,
No,you have to create new instance for new adconnect server in staging mode.
I recommend you to avoid using the SQL server already used for the first adconnect server to ensure the high availability in case of crash of SQL server.
take not , that when you import configuration settings exported from the first adconnect server , the second adconnect server will have the same configuration (rules, connectors..ect)
Migrate settings from an existing server
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