IBM Cognos Interview Questions & Answers (2025)

Cognos was an Ottawa company which is based on Ontario performance management software.

It has many advantages that are described below:

• It has the ability to design complex layouts with the use of different data sources.
• It shows faster results at lower costs.
• It can use a plethora of charts which includes cross tables, lines, gauges, bar charts and many more.
• It shows complete connectivity indifferent of an environment.
Cognos supports all RDBMS (Relational Database Management systems) to handle reporting data.
• It can perform on any operating system which means the user doesn't need to install again on changing the operating system.
• It creates reports very accurate, relevant and reliable.

Dynamic cubes are present in-memory Online Analytical Program (OLAP) which loads data from the relational data source.

• It is built in schemes like star or snowflake.
• It is introduced in the versions IBM Cognos BI 10.2 or above.
• It is the technology of IBM Cognos BI query stack.
• Its main purpose is to a response regarding reports and studies on a great volume of data.
• It enables the high performance for interaction and studies the data.

Aggregate Advisor help in increasing the overall performance.

• It is a component of the Dynamic Query Analyzer
• It can be Support database either in-memory aggregate or aggregate tables or maybe both.
• Aggregate Advisor utilize statistics and cube’s model
• Aggregate Advisor utilize workload log files which are available from the execution of reports
• To recover the summed value and put the values in their specific aggregate cache so that they can be used for query processing, aggregate execute the important SQL statement after the cube restart.
• It works during the off-peak meanwhile in the non-critical business hours

Cognos Dynamic Cube encourages two types of pre-computed aggregate values and these are

1. Saved in in-database tables
2. Saved in an in-memory aggregate cache
• An aggregate advisor can hold a factory of in-memory aggregates and further in-memory aggregates do not need the DBA.
• Instructions are saved in the "Content Manager" and when a cube is started after this, it is affected.
• The properties of a dynamic cube decide the fate of the size of the aggregate cache that is the highest amount that can be used by the aggregate cache.

To be considered a durable model, it needs to follow some criteria and these are given below.

1. It is always a design language that is built up for the model which is different from the areas the clients can select from. As an example, English (Zimbabwe) is assigned for the language English.
2. The name of the languages of other than the design language can be changed if required but for design language, it is not possible to change namespaces, query items, query languages that are published in a package.
3. It is not possible to change the structure of the published package's query subject, query items, dimensions, namespace(s), shortcuts etc. The reason behind this is that the structure is kept in specification's definition with design language's name.
4. The element must be in model.xml in the version IBM Cognos 8.4.1.

Following are the ways to change non-durable models into durable model

• In the case of the model does not have a design language, then the steps are-
• It is the vital part of the method to attach the design language to the model. After that combine it to the languages of each package which is on the basis of the model. When it is done, save and close the model.
• Open the model.xml file with the help of using XML or text editor. After that modify the value to en-zw from en which is present near the top of the file.
• If you are using IBM Cognos 8.4.1 you need to add a blank line into the model.xml file which is located just under the modified element. When it is done, insert true to the new blank line.
• If you are using IBM Cognos 10 you need to fix the project level property. It is advised to make use of Design Locale for Reference ID to a value of true.

• It is possible to analyze, monitor and report on information that is collected from different devices with the help of IBM Predictive Maintenance and Quality. Moreover, you can get the information regarding the actions from Predictive Maintenance and Quality.
• IBM Predictive Maintenance and Quality can employ to accomplish the following assignments:
• It is helpful in preventing costly unexpected break by earlier prediction of failure of any instrumented.
• It makes the changes in the maintenance to diminish break and help in reducing the cost of repair.
• It looks after the least costly and most powerful solution to the problem by maintaining the logs. It also helps in maintaining the cycles.
• It goes to the root of the cause of the problem vigorously so that clients can take suitable action to repair it.
• It determines the safety, security and quality issue to minimize the chances of failure.

It is a tool which is defined in Cognos to extract and transform the data from different data sources to target data sources.

It indicates the group of users who have the same rights and required to access the same data. It is the duty of the administrator to build the user class and catalog. This job of the creating and maintaining user class can also be performed by the other users of the organization in their geographical area.

You are also able to build a catalog and you can add the user to it. You can also add the users to the personal copy of a distributed catalog. You will get all the rights from the administrator so you can insert or make changes of user classes

A catalog is a file which contains information such as folders, columns, conditions, etc. on the database tables. The highlighted point here is that it doesn’t contain any data instead it contains metadata definitions and table structures. It has mainly four types:

• Personal Catalog: It is a type of catalog in which only one user can create or modify a catalog or report.
• Shared Catalog: In this, one user (creator) can create the catalog but other users can also create their own reports with the use of this catalog.
• Distributed Catalog: In this, anyone can change or modify their own created distributed catalogs and can also make their own reports.’
• Secured Catalog: In this type of catalog, no one can modify the reports or catalogs. They are fully secured.

It is the studio in which Cognos perform its Ad-hoc queries.

There are many types of indexes used in Cognos. These are:

• Bitmap Indexes: A bitmap index is used to replace a list of rowids with the key values. Due to the presence of low cardinality and low updates, it is more efficient for data waring.
• B-tree indexes: B-tree indexes are used on the availability of high-cardinality, generally when we have too many distinct columns. It is mainly used for OLTP.
• Function-based indexes: These are created on the results of an expression or function.
• Reverse key and Composite Indexes: In the reverse key, the keys of an index are reversed and then stored.

The Cognos gateway is a point or starting point where the first request received and then send to the BI server. Cognos gateways used to encrypt the request adds necessary updating like variables or namespaces and then transfers the information to application servers.

The following gateways are supported by Cognos:

• CGI: It stands for Common Gateway Interface known as the default gateway. It is a basic gateway.
• ISAPI: This is called an Internet Service Application Interface which is for the windows environment. It is best suitable for windows IIS (Internet Information Service)
• Servlet: This gateway is suitable for those application servers who supports servlets.
• Apache_mod: This gateway is used for Apache servers.

It is used to find the hidden patterns and trends of data.

It is possible for the users to make data sources with the help of the framework manager within the several Cognos series. It also allows users to add details and logic. A framework manager is a reservoir of information and logic that can be used in a data source in a logical Cognos architecture.

The Framework Manager model comprises of three different layers:

• Database layer
• Logical Layer
• Dimensional layer

There are different types of securities that can be applied in Framework manager.

• Data Security: It is used to secure the data in framework manager. In this, first, you create a security filter which is then applied to a specific query. The process involves the control of data which is done by the filter. This checks the data to be shown to the users when they set up their reports.
• Object Security: It is able to secure the object just by supporting the users access to the object, by keeping hidden from the users and by rejecting users access to the object.
• Package Security: In this kind of security, the user is able to apply security to a package and can check who has access to the package.

Two types:

Sequential: which runs the session one by one.

Concurrent: Which runs the sessions simultaneously

The different types of the report in Cognos are:

• Chart report
• List report
• Blank report
• Repeater report
• Cross report

It is used to create advanced business reports.

These are mainly of three types:

• Standard Folder
• Package Folder
• Metrics Folder

The main differences between the Cognos Dynamic cube and Transformer/TM1 cube and PowerPlay cube are: