ORA-17627: ORA-01017: invalid username/password; logon denied

 If you are doing a duplicate database from active database and commands fails with a combination of ORA-17627: ORA-01017, as follows

RMAN> duplicate target database to dupdb from active database;  Starting Duplicate Db at 23-FEB-18 using target database control file instead of recovery catalog allocated channel: ORA_AUX_DISK_1 channel ORA_AUX_DISK_1: SID=4201 device type=DISK allocated channel: ORA_AUX_DISK_2 channel ORA_AUX_DISK_2: SID=4306 device type=DISK allocated channel: ORA_AUX_DISK_3 channel ORA_AUX_DISK_3: SID=4411 device type=DISK allocated channel: ORA_AUX_DISK_4 channel ORA_AUX_DISK_4: SID=4516 device type=DISK current log archived at primary database contents of Memory Script: {    sql clone "create spfile from memory"; } executing Memory Script   sql statement: create spfile from memory contents of Memory Script: {    shutdown clone immediate;    startup clone nomount; } executing Memory Script Oracle instance shut down connected to auxiliary database (not started) Oracle instance started Total System Global Area   25654751232 bytes Fixed Size                     2265224 bytes Variable Size               7784632184 bytes Database Buffers           17649631232 bytes Redo Buffers                 218222592 bytes contents of Memory Script: {    sql clone "alter system set  db_name =  ''PRODDB'' comment=  ''Modified by RMAN duplicate'' scope=spfile";    sql clone "alter system set  db_unique_name =  ''DUPDB'' comment=  ''Modified by RMAN duplicate'' scope=spfile";    shutdown clone immediate;    startup clone force nomount    backup as copy current controlfile auxiliary format  '+ORADATA/dupdb/control01.ctl';    alter clone database mount; } executing Memory Script   sql statement: alter system set  db_name =  ''PRODDB'' comment= ''Modified by RMAN duplicate'' scope=spfile   sql statement: alter system set  db_unique_name =  ''DUPDB'' comment= ''Modified by RMAN duplicate'' scope=spfile   Oracle instance shut down   Oracle instance started   Total System Global Area   25654751232 bytes   Fixed Size                     2265224 bytes Variable Size               7784632184 bytes Database Buffers           17649631232 bytes Redo Buffers                 218222592 bytes   Starting backup at 23-FEB-18 allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=4730 instance=opera1 device type=DISK allocated channel: ORA_DISK_2 channel ORA_DISK_2: SID=4835 instance=opera1 device type=DISK allocated channel: ORA_DISK_3 channel ORA_DISK_3: SID=4940 instance=opera1 device type=DISK allocated channel: ORA_DISK_4 channel ORA_DISK_4: SID=5045 instance=opera1 device type=DISK channel ORA_DISK_1: starting datafile copy copying current control file RMAN-00571: =========================================================== RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ============== RMAN-00571: =========================================================== RMAN-03002: failure of Duplicate Db command at 02/23/2018 14:39:46 RMAN-05501: aborting duplication of target database RMAN-03015: error occurred in stored script Memory Script RMAN-03009: failure of backup command on ORA_DISK_1 channel at 02/23/2018 14:39:46 ORA-17629: Cannot connect to the remote database server ORA-17627: ORA-01017: invalid username/password; logon denied ORA-17629: Cannot connect to the remote database server

You probably need to check following
·       Make sure that password of target database and duplicate database is same.
·       Has the password file for duplicate database been created using orapwd utility and you are using  correct password during RMAN initiation.
·       Open sqlplus on both target and duplicate database host and check connectivity with sys user using TNS entries defined above.