Idle time slowness after 19c upgrade

Hi All,

we recently upgraded DB from 11g R2 to 19c. After upgrade, we experience slowness issue in our work environment.

for ex:

1) Establish a SQL*Plus connection to the instance:

2) Leave this SQL session idle for an hour.

3) Return to the client and issue a simple select statement:

-- select * from v$tempfile; --> elapsed time is 46 seconds and the waitevent is "controlfile sequential read"

next execution is fast

after 5 minutes is fast

after 10 minutes is fast

wait another 1 hour additionally and it's slow again

Do anyone experience these type of issue, any input is appreciated.