CTRL_FILE_RECORD_KEEP_TIME

The control file contains two types of records: Circular reuse records and Noncircular reuse records

Circular reuse records contain noncritical information that is eligible to be overwritten if needed. These records contain information that is continually generated by the database. When all available record slots are full, the database either expands the control file to make room for a new record or overwrites the oldest record. The CONTROL_FILE_RECORD_KEEP_TIME initialization parameter specifies the minimum age in days of a record before it can be reused.

Noncircular reuse records contain critical information that does not change often and cannot be overwritten. Some examples of information in noncircular reuse records include datafiles, online redo log files, and redo threads.As you make backups of a target database, the database records these backups in the control file. To prevent the control file from growing too large because of the addition of new records, records can be reused if they are older than a threshold you specify. The CONTROL_FILE_RECORD_KEEP_TIME initialization parameter determines the minimum age in days of a record before it can be overwritten:

CONTROL_FILE_RECORD_KEEP_TIME = integer

For example, if the parameter value is 7, then any record aged 7 days and older is a candidate for reuse. Information in an overwritten record is lost. The oldest record available for reuse will be used first.

When the database needs to add new RMAN repository records to the control file, but no record is older than the threshold, the database attempts to expand the size of the control file. If the underlying operating system prevents the expansion of the control file (due to a disk full condition, for instance), then the database overwrites the oldest record in the control file.

The database records the overwrite in the alert log located in the Automatic Diagnostic Repository (ADR). For each record that it overwrites, the database records an entry in the alert log similar to the following:

kccwnc: following control file record written over: 

RECID #72 Recno 72 Record timestamp 

07/28/06 22:15:21 

Thread=1 Seq#=3460 

Backup set key: stamp=372031415, count=17 

Low scn: 0x0000.3af33f36 

07/27/06 21:00:08 

Next scn: 0x0000.3af3871b 

07/27/06 23:23:54

Resetlogs scn and time 

scn: 0x0000.00000001