Incarnation is different between Primary and Standby

Despite successfully cloning your Primary Database using RMAN, it is possible that when you
attempt to start the Managed Recovery Process (MRP) on the Physical Standby, it fails to the
following error seen in the database instance alert log:
ORA-19909: datafile 1 belongs to an orphan incarnation
This is due to the Primary Database having only 1 incarnation, while the Standby has many, as
seen below:
RMAN> list incarnation;
using target database control file instead of recovery catalog
List of Database Incarnations
DB Key  Inc Key DB Name  DB ID   STATUS  Reset SCN  Reset Time
------- ------- -------- ---------------- --- ---------- ----------1   1   PRD   2067014306   PARENT  1   29-OCT-09
3     3   PRD   2067014306   ORPHAN  1385720549 28-APR-10
2   2   PRD   2067014306   CURRENT 13173291621 28-JUN-10
The ORA-19909 error can occur if the RMAN clone has been performed before, or the Standby
Database has been flashed back.
Solution
The solution is to find out the CURRENT incarnation from the Primary Database and reset the
Standby Database incarnation to match, using the following RMAN command:
reset database to incarnation <key>
then perform Recovery.
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E.g.
On the Standby Site:
rman target=/
RMAN > reset database to incarnation 1
RMAN > exit
sqlplus / as sysdba
SQL> alter database recover managed standby database disconnect from session;