What type of files are C-9999-yyyymmdd-00 in Oracle At my {ORACLE_HOME}\database I found like 3GB of this type of files:



I think they are not backup of controlfile because size of files changes over time.
They're control file backups.

The reason for the file size discrepencies is due to the fact that they're for different databases. Order the list by filename and it'll be more obvious. Just for your information, the first number after the C- prefix is the DBID (database ID).