Explanation:
The default value of the initialization parameter CONTROL_FILE_RECORD_KEEP_TIME is seven days. The value set for this parameter determines the number of days the record must be maintained in the target database’s control file before it can be reused. It specifies the minimum number of days before a reusable record in the control file can be reused. In the event a new record needs to be added to a reusable section and the oldest record has not aged enough, the record section expands. If this parameter is set to 0, then reusable sections never expand, and records are reused as needed.
Reference:
Oracle 9i Net Services Administrator’s Guide
Oracle 9i Net Services Reference Guide
Oracle 9i Recovery Manager Reference
Oracle 9i Backup and Recovery Concepts

---