slowness in query execution in Active Dataguard (readonly) OCI - DBCS (12.1.0.2.0)

Summary:

We have ADG for our Production environment and reports are running very slow in this environment, kindly advice how to tune the performance

DB Role: PHYSICAL STANDBY (READ ONLY WITH APPLY)

DB Version: 12.1.0.2.0 (OCI - DBCS)

Content (required):

ADG (readonly) environment query performance is very slow and same query was executed in Standalone DBCS environment is very smooth and fast

Version (include the version you are using, if applicable):

Active Dataguard - DB Version: 12.1.0.2.0 (OCI - DBCS)

Code Snippet (add any code snippets that support your topic, if applicable):