KB15977: 'User request is queued. Maximum cache memory usage has been reached for existing caches' error occurs when a user tries to execute a report from the History List in MicroStrategy Intelligence Server

SYMPTOM
When a user tries to execute a report from the History List in Strategy Intelligence Server, the following error is seen:

Maximum cache memory usage has been reached for existing caches. It could be that the report result is too big. Please try later or contact your Administrator.​

 
The following error is found in the DSSErrors.log:
 

ReportCacheAdmin::AddInboxRefCount() return error = 0x40041E13 for msg <ID>

STEPS TO REPRODUCE
Follow the steps below to reproduce this issue:

1. Go to Project Configuration > Caching > Result Caches > Storage.
2. Set the Maximum RAM Usage (MBytes) setting to 1MB.
3. Log in into Strategy Web.
4. Execute a large report (so that the cache size is greater than 1MB) and send it to the History List.
5. Log out from Strategy Web 
6. Log in into Strategy Web again.
7. Go to the History List.
8. Execute the report previously sent to the History List.
9. The errors described above will occur.

CAUSE
This occurs when a user tries to bring a report back from the History List that is bigger in size than the Maximum RAM Usage (MBytes) governing setting for caches for the project. Since the Strategy Intelligence Server is trying to load a history cache file into RAM that is governed by the setting, it throws the error. This is working as designed.
 
ACTION
Increase the Maximum RAM Usage (MBytes) governing setting for caches for the project to something greater than the size of the report that was sent to the History List.