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CONFIGURE SNAPSHOT CONTROLFILE NAME TO'C:\ APP\ ADMINISTRATOR\ VIRTUAL\ PRODUCT\ 12.2.0\ DBHOME_2\ DATABASE\ SNCFNEWTEST.ORA'; # default

RMAN > show snapshot controlfile name

The RMAN configuration parameters of the database for which db_unique_name is NEWTEST are:

CONFIGURE SNAPSHOT CONTROLFILE NAME TO'C:\ APP\ ADMINISTRATOR\ VIRTUAL\ PRODUCT\ 12.2.0\ DBHOME_2\ DATABASE\ SNCFNEWTEST.ORA'; # default

RMAN > backup tablespace system tag=system_tbs_bak

Starting with backup, which is located in 02-February-18

Use channel ORA_DISK_1

Channel ORA_DISK_1: starting backup set of all data files

Channel ORA_DISK_1: specifying data files in the backup set

Enter the data file, file number = 00001 name = C:\ APP\ ADMINISTRATOR\ VIRTUAL\ ORADATA\ NEWTEST\ SYSTEM01.DBF

Channel ORA_DISK_1: starting segment 1 from 02 to February-18

Channel ORA_DISK_1: completed startup segment 1 from 02 to February-18

Fragment handle = E:\ RECOVERYFLASH\ NEWTEST\ BACKUPSET\ 2018'02'02\ O1_MF_NNNDF_SYSTEM_TBS_BAKF77L95QK.BKP tag = SYSTEM_TBS_BAK comment = NONE

Channel ORA_DISK_1: backup set completed, time: 00:00:35

Completed backup in 02-February-18.

The snapshot control file is a copy of the current control file generated by the RMAN recovery manager at a specified location on the system

We know that control files change constantly throughout the database lifetime, and RMAN backups need to rely on control files or recovery directories, that is to say, you need to know that backup is on

The original checkpoint SCN and all file structure information and need to be consistent throughout the backup, but the control file cannot be locked (the lock operation cannot perform the checkpoint, cut

Change the log, etc.). Therefore, it is necessary to maintain consistency without affecting the normal operation of the database. Snapshot control files emerge as the times require. RMAN only controls the actual text during a backup or synchronization operation

Component makes a brief lock and generates or refreshes the snapshot control file based on its contents. Once this action is completed, RMAN will switch to using snapshot control files for backup and synchronization

Operation. So as to ensure the consistency of control files, data files and so on during the backup.

To sum up, its main function is to use RMAN to synchronously restore directories or backups to get a consistent control file.

As can be seen from the above tests

-- An and RMAN start the backup. Oracle checks whether the control file is consistent with the snapshot control file (if it does not exist, extract information from the control file to create it), and refresh the snapshot control file if it is inconsistent.

-- b and RMAN read the information from the snapshot control file for backup, which does not contain the new tablespace, so there is no tbs_test.dbf in the backup set

C. Automatic backup of control files and spfile files after the backup is completed.

-- d. Refreshed snapshot control files

-- e, so the above detection control files, snapshot control files, backup control files all contain information about the new tablespace. However, there is no backup because the tablespace is added after the backup begins.

-- adjust the location of snapshot control files to the default path

RMAN > configure snapshot controlfile name clear

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