GCMS is a new system that is replacing old CAIPS system and its more effective. They are upgrading it recently and transfering files to GCMS so errors are being generated.
CIC's eCAS or eclient system allows you to check the status of your Canada immigration application online at no cost.
It doesn't actually provide much information about your application, usually just what stage of processing it has reached and whether a decision has been made.
eCAS is a term that often refers to by the terms FOSS & CAIPS notes
http://immipedia.ca/CAIPS
Global Case Management System GCMS is the "new" system (it has been a project of the Canadian government for many years.
Cost estimate $200 million.
The system allows extensive free form text notes for users (not the public) - and many other undisclosed "clever" things that will aid fraudulent activity.
Transfer of data from ecas has been happening for a while now.