Some URL, which length can be over 2500 characters, trigger an HTTP error 413.
The 413 status code indicates that the request was larger than the server is able to handle, either due to physical constraints or to settings.
Internet Explorer browser has a limitation of maximum 2,083 characters in the URL. And this issue is due to this size limitation.
When Cookie Provider is configured, then SiteMinder sends the SMSESSION cookie in the URL itself after returning from Cookie Provider. And This Smsession Cookie is roughly (1000~1400 Characters).
Now because IE has a max URL size limitation of 2083 characters, out of which around (1000~1400) characters are consumed by SiteMinder Smsession cookie, so this means that the application can have around (500~700) characters in the URL. Therefore, if the application URL is bigger than that, then the Return URL from Cookie Provider exceeds this 2,083 characters limit and hence breaks the functionality of Web Agent.
We cannot modify/reduce the size of SMSESSION cookie.
The only option you have is to use any other browser than IE as this size restriction is imposed only by IE and other browsers do not impose this restriction.