While running ADOP I saw below error in adconfig log file.

Error:

ORA-12516: TNS:listener could not find available handler with matching protocol stack

CAUSE;

 This is an issue with the number of database process/sessions. 

SOLUTION:

We can check utilization of processes and session.

 SQL>  select resource_name, current_utilization, max_utilization from v$resource_limit where resource_name in ('processes','sessions');

RESOURCE_NAME                  CURRENT_UTILIZATION MAX_UTILIZATION
------------------------------ ------------------- ---------------
processes                                      478             500
sessions                                       499             540


We can bounce the database, and increase the number of processes/sessions . Re-run the patch application.


Reference: adop fails with "ORA-12516: TNS:listener could not find available handler with matching protocol stack" (Doc ID 2105049.1)