After upgrade of our testing database to 12cR1 (12.1.0.2 + PSU April 15) I've got a claim that database is not performing well, moreover login process takes significant long time.

I did several upgrades before but this one was first RAC database. During review of performance I've found a main difference between single instance database and RAC. Each session has performed these two queries:

 

SQL_ID        SQL_FULLTEXT
------------- --------------------------------------------------------------------------------
frjd8zfy2jfdq SELECT executions, end_of_fetch_count,              elapsed_time/px_servers elap
              sed_time,        cpu_time/px_servers     cpu_time,            buffer_gets/execut
              ions  buffer_gets   FROM (SELECT sum(executions)   as executions,
                           sum(case when px_servers_executions > 0
                then px_servers_executions                                  else executions en
              d) as px_servers,                sum(end_of_fetch_count) as end_of_fetch_count,
                           sum(elapsed_time) as elapsed_time,                 sum(cpu_time)
                as cpu_time,                     sum(buffer_gets)  as buffer_gets            F
              ROM   gv$sql                                      WHERE executions > 0
                                     AND sql_id = :1                                    AND pa
              rsing_schema_name = :2)



SQL_ID        SQL_FULLTEXT
------------- --------------------------------------------------------------------------------
4b4wp0a8dvkf0 SELECT executions, end_of_fetch_count,              elapsed_time/px_servers elap
              sed_time,        cpu_time/px_servers     cpu_time,            buffer_gets/execut
              ions  buffer_gets   FROM (SELECT sum(executions_delta) as EXECUTIONS,
                                 sum(case when px_servers_execs_delta > 0
                            then px_servers_execs_delta
              else executions_delta end) as px_servers,                sum(end_of_fetch_count_
              delta) as end_of_fetch_count,              sum(elapsed_time_delta) as ELAPSED_TI
              ME,              sum(cpu_time_delta) as CPU_TIME,                      sum(buffe
              r_gets_delta) as BUFFER_GETS          FROM   DBA_HIST_SQLSTAT s,
                                 V$DATABASE d,                                         DBA_HIS
              T_SNAPSHOT sn                           WHERE  s.dbid = d.dbid
                              AND  bitand(nvl(s.flag, 0), 1) = 0                    AND  sn.en
              d_interval_time >                                   (select systimestamp at TIME
               ZONE dbtimezone                  from dual) - 7                               A
              ND  s.sql_id = :1                                    AND  s.snap_id = sn.snap_id
                                         AND  s.instance_number = sn.instance_number
               AND  s.dbid = sn.dbid                                 AND  parsing_schema_name
              = :2)