Ccl-bit-0006 the http message is unexpectedly short

Cognos BI 10.1.1
Cognos TM1 9.5.2
Windows 2008 R2 Server

Some Cognos BI reports have stopped to work. They worked fine last month.
They give strange error about WebSphere, but this a Windows installation with default Cognos BI built-in tomcat engine.

Error Message:
ccl-bit-0006 the http message is unexpectedly short
The connection closed before the request is processed. If you are using WebSphere Application Server, to reduce the frequency of this error, increase the Persistent Timeout parameter for the Web container transport chains in the administrative console. Increase the time in 10-15 second intervals until the error no longer or rarely occurs

The error message is because the report process timeouts, but this can be of different issues.
In this case it is the TM1 application who disconnect the reports users process direct at start of the report.

If you time with a stop watch from you press RUN in the report after the prompt page, until the error message. If that is exactly 60 seconds, then it is Cognos BI that have time out.

You need to investigate further to find why the report does not work.

If the report is getting data from a TM1 cube, run the TM1TOP utility to that cube and monitor what happens when the report is run.

If you want to change the timeout value in Cognos BI - do this:
1. Navigate to the <IBMCOGNOS home>/tomcat/conf directory
2. Open server.xml
3. Locate the following entry:
<!-- Define a non-SSL Coyote HTTP/1.1 Connector on port 8080 -->
<Connector className="org.apache.coyote.tomcat4.CoyoteConnector" port="9300" minProcessors="5" maxProcessors="75" enableLookups="true" redirectPort="9443" acceptCount="100" debug="0" connectionTimeout="60000" useURIValidationHack="false" disableUploadTimeout="true"/>
<!-- Note : To disable connection timeouts, set connectionTimeout value
to -1 -->

<!-- A "Connector" represents an endpoint by which requests are received
and responses are returned. Documentation at :
Java HTTP Connector: /docs/config/http.html (blocking & non-blocking)
Java AJP Connector: /docs/config/ajp.html
APR (HTTP/AJP) Connector: /docs/apr.html
Define a non-SSL HTTP/1.1 Connector on port 8080
<Connector port="9300" protocol="HTTP/1.1"
4. Change the connectionTimeout value from 60000 to xxxxxx (in milliseconds)
5. Save server.xml
6. Restart Cognos BI service
If the TM1 cube is feed with data from Cognos Controller, any change to dimensions/accounts will be transferred over to the TM1 cube. If a report is built with the dimension name in Cognos Report Studio - that report will not know of the change of dimensions name, and stop working.

When the Cognos BI report ask for a field that does not exist, the TM1 Application disconnects the connection. And the Cognos BI Report will timeout.

Run the report for different months - does it work for older months?
Make a copy of the Cognos BI report.
Remove parts of the Cognos BI report and run it again.
Repeat above until you find the part that is making the report not to work.
Check that value in the TM1 cube.
Have it changed since last month ?

Rebuild the report to contain correct fields/dimensions names.