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Cognos BI architecture

The IBM Cognos 10.2 BI architecture is separated into the following three tiers:

  • Web server (gateways)
  • Applications (dispatcher and Content Manager)
  • Data (reporting/querying the database, content store, metric store)

Web server (gateways)

The user starts a web session with Cognos to connect to the IBM Cognos Connection’s web-based interface/application using the web browser (Internet Explorer and Mozilla Firefox are the currently supported browsers). This web request is sent to the web server where the Cognos gateway resides.

The gateway is a server-software program that works as an intermediate party between the web server and other servers, such as an application server. The following diagram shows the basic view of the three tiers of the Cognos BI architecture:

The Cognos gateway is the starting point from where a request is received and transferred to the BI Server. On receiving a request from the web server, the Cognos gateway applies encryption to the information received, adds necessary environment variables and authentication namespace, and transfers the information to the application server (or dispatcher).

Similarly, when the data has been processed and the presentation is ready, it is rendered towards the user’s browser via the gateway and web server. The following diagram shows the Tier 1 layer in detail:

The gateways must be configured to communicate with the application component (dispatcher) in a distributed environment. To make a failover cluster, more than one BI Server may be configured.

The following types of web gateways are supported:

  • CGI: This is also the default gateway. This is a basic gateway.
  • ISAPI: This is for the Windows environment. It is the best for Windows IIS (Internet Information Services).
  • Servlet: This gateway is the best for application servers that are supporting servlets.
  • Apache_mod: This gateway type may be used for the Apache server.

The following diagram shows an environment in which the web server is load balanced by two server machines:

To improve performance, gateways (if more than one) must be installed and configured on separate machines.

The application tier (Cognos BI Server)

The application tier comprises one or multiple BI Servers. A server’s job is to run user requests, for example, queries, reports, and analysis that are received from a gateway.

The GUI environment (IBM Cognos Connection) that appears after logging in is also rendered and presented by Cognos BI Server. Another such example is the Metric Studio interface.

The BI Server must include the dispatcher and Content Manager (the Content Manager component may be separated from the dispatcher). The following diagram shows BI Server’s Tier 2 in detail:

Dispatcher

The dispatcher has static handlers to many services. Each request that is received is routed to the corresponding service for further processing.

The dispatcher is also responsible for starting all the Cognos services at startup. These services include the system service, report service, report data service, presentation service, Metric Studio service, log service, job service, event management service, Content Manager service, batch report service, delivery service, and many others.

When there are multiple dispatchers in a multitier architecture, a dispatcher may also send and route requests to another dispatcher. The URIs for all dispatchers must be known to the Cognos gateway(s).

All dispatchers are registered in Content Manager (CM), making it possible for all dispatchers to know each other. A dispatcher grid is formed in this way.

To improve the system performance, multiple dispatchers must be installed but on separate computers, and the Content Manager component must also be on a separate server. The following diagram shows how multiple dispatcher servers can be added.

Services for the BI Server (dispatcher)

Each dispatcher has a set of services, which are listed alphabetically in the following table. When the Cognos service is started from Cognos Configuration, all services are started one by one.

The following table shows the dispatcher services and their short descriptions:

Service

Description

Agent service

Runs the agent.

Annotation service

Adds comments to reports.

Batch report service

Handles background report requests.

Content manager cache service

Handles cache for frequent queries to enhance performance of Content Manager.

Content manager service

Performs DML in content store db. Cognos deployment is another task for this service.

Delivery service

For sending e-mails.

Event management service

Manages the Event Objects (creation, scheduling, and so on)

Graphics service

Renders graphics for other services such as report service.

Human task service

Manages human tasks.

Index data service

For basic full-text functions for storage and retrieval of terms and indexed summary documents.

Index search service

For search and drill-through functions, including lists of aliases and examples.

Index update service

For write, update, delete, and administration-related functions.

Job service

Runs jobs in coordination with the monitor service.

Log service

For extensive logging of the Cognos environment (file, database, remote-log server, event viewer, and system log).

Metadata service

For displaying data lineage information (data source, calculation expressions) for the Cognos studios and viewer.

Metric studio service

This service is used for providing a user interface to metric studio for monitoring and manipulating system KPIs.

Migration service

Used for migration from old versions to new versions, especially series 7.

Monitor service

Works as a timer service-it manages the monitoring and running of tasks that were scheduled or marked as background tasks. Helps in failover and recovery for running tasks.

Presentation service

This service prepares and displays the presentation layer by converting the XML data to HTML or any other format view. IBM Cognos Connection is also prepared by this service.

Query service

For managing dynamic query requests.

Report data service

This service prepares data for other applications; for example mobile, Microsoft Office, and so on.

Report service

Manages report requests. The output is displayed in IBM Cognos Connection.

System service

This service defines the BI-Bus API compliant service. It gives more data about the BI configuration parameters.

Summary

This article covered the IBM Cognos BI architecture. Now you must be familiar with the single tier and multitier architectures and a variety of features and options that Cognos provides.

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