Cognos Architecture

Cognos is a multi-tiered architecture with a Web Tier, Application Tier and Data Tier. These three tiers are separated by network firewalls.

Web Tier: web communication in Cognos happens through gateways. A gateway is an extension of web server program that transfers information from the web server to application server. Web communication can also occur directly with dispatcher however, it has some limitations.

CGI is the default gateway which is commonly used for all supported web servers. For enhanced performance, we use following:  

• ISAPI can be used with Microsoft IIS web server. It delivers faster performance for IIS.

•  Apache_Mod can be used with Apache web server.

• Servlets can also be used as gateways

Application Tier: it includes a Dispatcher and a Content Manager. 

Dispatcher: it operates and starts all Cognos services and routes requests. It is a multi-threaded application that uses one or more threads to handle a request. It can route requests to a report service, presentation service, job service or monitor service etc.

• A dispatcher can also route requests to another dispatcher based on load balancing needs or package or user group requirements.

• While configuring gateways, we can list the URIs of target dispatchers in the order of most to least preferred. If one dispatcher fails, requests are routed to another dispatcher based on this list.

• When a dispatcher starts, it registers itself with Content Manager. In this way, each dispatcher is aware of other dispatchers. If one dispatcher fails or unavailable, requests are automatically routed to next available dispatcher until the failed dispatcher registers itself.

• Whenever we made configuration changes, it will be communicated to dispatcher. Dispatcher includes Cognos firewall to maintain security.  

Content Manager: it manages content store which contains application data including security, configuration data, models, metrics, report specifications, and report outputs. In reality, we may have more than one Content Manager each on a different server. At any point of time only one Content Manager will be active and remaining will be on Standby. 

Content Manager stores following information:

• Reports: specifications, properties, security settings, and outputs.
• Report Packages
• Metric Packages
• Agents: schedules and tasks used to monitor events.
• Server Configuration: contacts, distribution lists, data sources and printers
• Personal User Information: My folders, My pages
• Language Information: names, descriptions and tool tips in different languages.