"Either the start snapshot %s or the end snapshot %s is incomplete or missing key statistics."
*Cause: Either the start or the end snaphots was missing or purged
or had encountered errors while creating them.
*Action: Verify that AWR is done taking these two snapshots, or
Look in DBA_HIST_SNAP_ERROR to find what tables are missing
in the start/end snapshots.
Use the ERROR_NUMBER column in that view together with the
alert log to identify the reason for failure and take
necessary action to prevent such failures in the future.
Try running ADDM on a different snapshot range that has
valid start and end snapshots.