RMAN-04006 from auxiliary database

Error:

Getting below error while "DUPLICATE TARGET DATABASE FOR STANDBY FROM ACTIVE DATABASE"

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00554: initialization of internal recovery manager package failed
RMAN-04006: error from auxiliary database: ORA-12528: TNS:listener: all appropriate instances are blocking new connections

Cause:

Service handler is blocking connections.

Solution:

Append (UR=A) clause in "CONNECT_DATA=" section of TNS to allow a privileged or administrative user to connect via listener

Example:

UAT =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = uatdb01)(PORT = 1529))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = UAT)
  (UR = A)
    )