> (you don't have to strictly follow this form)

**Use case**

Sometimes, for really sophisticated scenarios it can be hard to control the amount of in-progress backups run externally. For the purpose of simpler control we can introduce server-level setting which disallows running concurrent backups of any type. 

Something like this in `config.xml` (enabled by default):
`<allow_concurrent_backups>true</allow_concurrent_backups>`

**Describe the solution you'd like**

It's important that backups can be executed in distributed way on multiple servers. Need to take it into account.

**Describe alternatives you've considered**
External check of `system.backups` table, but it can be complex.

size_t replica_num_in_backup = 0;
    
    
    
    bool allow_non_empty_tables = false;
    
    RestoreAccessCreationMode create_access = RestoreAccessCreationMode::kCreateIfNotExists;
    
    
    bool allow_unresolved_access_dependencies = false;
    
    RestoreUDFCreationMode create_function = RestoreUDFCreationMode::kCreateIfNotExists;
    
    bool internal = false;
    
    
    String host_id;
    
    
    std::vector<Strings> cluster_host_ids;
    
    
    String coordination_zk_path;
    static RestoreSettings fromRestoreQuery(const ASTBackupQuery & query);
    void copySettingsToQuery(ASTBackupQuery & query) const;
};
}