clean flash recovery area archive logs
0) You have FRA configured, but it is not your archivelog destination.

Setting log_archive_dest_N to the FRA directory is not the same as actually setting the FRA as an archivelog destination.

The configuration you most likely have:

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      /oradata/flash_recovery_area
db_recovery_file_dest_size           big integer 20G
log_archive_dest_1                   string      location=/oradata/flash_recovery_area/qrec/archivelog


The proper configuration would be:

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      /oradata/flash_recovery_area
db_recovery_file_dest_size           big integer 20G
log_archive_dest_1                   string      location=use_db_recovery_file_dest


The naming of archivelog files also confirms this, as archivelogs in the FRA are use OMF format, and they are actually placed in seperate directories (named based on the date) each day.

So instead of this:

/oradata/flash_recovery_area/qrec/archivelog/log_1_1056_965658004.arc


The name of your archivelog file would be:

/oradata/flash_recovery_area/qrec/archivelog/2018_02_22/o1_mf_....arc


1) This is typically caused by inappropriate configuration of the control_file_record_keep_time parameter combined with a lacking backup method. The default value 7 means that records (of archivelogs or backups) are kept for 7 days, after that, they can be reused. If you do not backup/delete your archivelogs for 7 days, the database may reuse the controlfile records pointing to them, basically the database "forgets" these entries and leaves them in the filesystem.

You should regulary backup and delete your archivelogs and set control_file_record_keep_time appropriately based on your backup strategy.

If you use user-managed backups instead of RMAN, you need to take care of deleting these logs manually. RMAN can backup and delete these files in a single command.

2) Depends on your backup requirements.

If you use user-managed backups, make sure you have backups of these files, then delete them.

If you use RMAN, you can use catalog start with '/oradata/flash_recovery_area/qrec/archivelog/';, then use RMAN to backup and delete them.

If you do not need any backup of these files, simply delete them.