Hi
Country Chart of Account represent the account structured defined in Country Regulations.
in other words we can say that if company has to report as per their group company and report differently as per their local regulations.
This is the reason you can not use OCOA and CCOA as same.
It is not mandatory to assign both CCOA and OCOA. If reporting is different then both COA is to be used.
hope this helps!!!
Br,Vivek S