I got the error "ORA-20103: There are less than two snapshots in the specified time period".
What does that mean?
"There are less than two snapshots in the specified time period" means that an internal Performance Analysis process is waiting for the second snapshots to take place in order to create an advisory.
You will see the error when it finds only one snapshot. The process keeps sampling for the second snapshots and when it finds two snapshots an advisory is created.
ORA-20103 is an internal error message.
Error messages starting from -20000 until -20999 are user specified error messages.
Oracle provides these range of codes so applications can raise an application specific error, which will be displayed after the chosen code.
This is done using the raise_application_error PL/SQL function.