I will do the 2-system upgrade from OEM GC 11g (126.96.36.199.0) to Cloud Control 12c (188.8.131.52.0).
Under OEM GC 11g tab 'Developments' --> Enterprise Manager 12c Upgrade Console, on the top of this page, there is a warning message:
"Following required SMP plugin software is not uploaded to software dirctory: Oracle Beacon Plugin, Oracle Client System Analyzer, Oracle Database Plugin, Oracle Fusion Middleware Plugin, Oracle Management And Repository Plugin, Oracle OracleHome. Provide them and click Validate in Manage software page before taking repository backup. "
I am sure I have copied all plugin files (*.opar) that include all above 6 warning missing plugins. When I click the link 'Manage Software' under 'Preupgrade Steps' table, I input the absolutely path and click ‘Validate’ button, job was run and validation was success. But the warning message still exists. I click ‘Refresh Agents and Targets List’ and a job was run (RefreshAndValidateTargets_yyyy_mm_dd_hh_mi_ss_xxx) and the job got error:
Could not execute query: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (SYSMAN.PRE_UPGC_MASTER_AGENTS_PK) violated
ORA-06512: at "SYSMAN.PRE_UPG_CONSOLE", line 375
ORA-06512: at "SYSMAN.PRE_UPG_CONSOLE", line 346
ORA-06512: at line 1