Hi @Sayan,

From documentations:

"The Cloudera Manager minor version must always be equal to or greater than the CDH minor version because older versions of Cloudera Manager may not support features in newer versions of CDH. For example, if you want to upgrade to CDH 5.4.8 you must first upgrade to Cloudera Manager 5.4 or higher."

So, if you want to upgrade cdh to 5.15 first you have to upgrade Cloudera Manager to 5.15.

Best regards

Andrzej