ORA-38760: This database instance failed to turn on flashback database

 ORA-38760: This database instance failed to turn on flashback database

Solution:
SQL> startup mount;
 SQL> alter database flashback off;
Database altered.
SQL> shutdown immediate;
SQL>  startup
ORACLE instance started.

Total System Global Area 4294967296 bytes
Fixed Size                  3719064 bytes
Variable Size            1308622952 bytes
Database Buffers         2969567232 bytes
Redo Buffers               13058048 bytes
Database mounted.
Database opened.

Delete old file from /flashback/ directory.

 SQL> alter database flashback on;

Database altered.

RDA - Health Check / Validation Engine Guide (Doc ID 250262.1)

$./rda.sh -T hcve
Processing HCVE tests ...
Available Pre-Installation Rule Sets:
   1.  Oracle Database 10g R1 (10.1.0) Preinstall (Solaris)
   2.  Oracle Database 10g R2 (10.2.0) Preinstall (Solaris)
   3.  Oracle Database 11g R1 (11.1.0) Preinstall (Solaris)
   4.  Oracle Database 11g R2 (11.2.0) Preinstall (Solaris)
   5.  Oracle Database 12c R1 (12.1.0) Preinstallation (Solaris)
   6.  Oracle Identity and Access Management PreInstall Check: Oracle Identity
       and Access Management 11g Release 2 (11.1.2) Solaris
   7.  OAS PreInstall Check: Application Server 10g R2 (10.1.2) Solaris
   8.  OFM PreInstall Check: Oracle Fusion Middleware 11g R1 (11.1.1) Solaris
   9.  OFM PreInstall Check: Oracle Fusion Middleware 12c (12.1.3) Solaris
  10.  Oracle Forms and Reports PreInstall Check: Oracle Forms and Reports 11g
       Release 2 (11.1.2) Solaris
  11.  Portal PreInstall Check: Oracle Portal Generic
  12.  IDM PreInstall Check: Identity Management 10g (10.1.4) Solaris
  13.  BIEE PreInstall Check: Business Intelligence Enterprise Edition 11g
       (11.1.1) Generic
  14.  EPM PreInstall Check: Enterprise Performance Management Server (11.1.2)
       Generic
  15.  Oracle Enterprise Manager Cloud Control PreInstall Check: Oracle
       Enterprise Manager Cloud Control 12c Release 4 (12.1.0.4) Solaris
  16.  Network Charging and Control Preinstallation (Solaris)
  17.  Oracle E-Business Suite Release 11i (11.5.10) Preinstall (Solaris)
  18.  Oracle E-Business Suite Release 12 (12.1.1) Preinstall (Solaris)
  19.  Oracle E-Business Suite Release 12 (12.2.0) Preinstall (Solaris)

Available Post-Installation Rule Sets:
  20.  Data Guard Postinstall (Generic)
  21.  WLS PostInstall Check: WebLogic Server 11g (10.3.x) Generic
  22.  WLS PostInstall Check: WebLogic Server 12c (12.x) Generic
  23.  Portal PostInstall Check: Oracle Portal Generic
  24.  OC4J PostInstall Check: Oracle Containers for J2EE 10g (10.1.x) Generic
  25.  SOA PostInstall Check: Service-Oriented Architecture 11g and Later
       Generic
  26.  OSB PostInstall Check: Service Bus 11g and Later Generic
  27.  Oracle Forms 11g Post Installation (Generic)
  28.  Oracle Enterprise Manager Agent 12c Post Installation (Generic)
  29.  Oracle Management Server 12c Post Installation (Generic)
  30.  Network Charging and Control Database Post Installation (Generic)
  31.  Network Charging and Control 4.4 and later System Post Installation
       (Solaris)

Enter the HCVE rule set number or 0 to cancel the test
Press Return to accept the default (0)