13C OEM java.sql.SQLException: Connection Cache with this Cache Name does not exist

Perform the following steps on the OMS server as a work around

1. <OMS_HOME>/bin/emctl set property -name use_pooled_target_connections -value false

2. Restart oms

 <OMS_HOME>/bin/emctl stop oms -all

 <OMS_HOME>/bin/emctl start oms

Note: EM 13c: Target DB Home Page Shows 'Failed To Connect To The Target Database, Regions That Pull Real-time Data' (Doc ID 2474441.1)