Oracle Snapshot Control file (snapshot)

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 for the database db_unique_name for 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;

Start with backup at February-February-18
Using channel Ora_disk_1
Channel Ora_disk_1: Starting all data file backup sets
Channel Ora_disk_1: Specifying Data files in the backup set
Input data file, file Number = 00001 name = C:\APP\ADMINISTRATOR\VIRTUAL\ORADATA\NEWTEST\SYSTEM01. Dbf
Channel Ora_disk_1: February-February-18 Start Segment 1
Channel Ora_disk_1: Completed on February-February-18 Start Segment 1
Fragment handle = E:\RECOVERYFLASH\NEWTEST\BACKUPSET\2018_02_02\O1_MF_NNNDF_SYSTEM_TBS_BAKF77l95qk. BKP Mark = System_tbs_bak Comment = NONE
Channel Ora_disk_1: Backup set Complete, spents: 00:00:35
In February-February-18 completed the backup

A snapshot control file is a copy of the current control file generated by the Rman recovery manager at the specified location in the system
We know that control files are constantly changing throughout the life of the database, and Rman backups need to depend on the control file or the recovery directory, which means that the backup
At the beginning of the checkpoint SCN and all file structure information and this information needs to be consistent throughout the backup, but cannot lock the control file (the lock operation cannot perform checkpoints, cut
change logs, etc.). Therefore, it is necessary to maintain consistency without affecting the normal operation of the database. Snapshot control files came into being. Rman only the actual control text during a backup or synchronization operation
To create or refresh a snapshot control file based on its contents. Once the action is complete, Rman switches to use the snapshot control file for backup and synchronization
Operation. This ensures consistency of control files, data files, etc. during backup.
In summary, its main role is to use Rman Synchronous recovery directory or backup can get a consistent control file.
--from the above test,
--a, RMAN starts the backup, the Oracle checks whether the control file is consistent with the snapshot control file (if it does not exist, from the control file extraction information is created), and the snapshot control file is refreshed without inconsistency.
--b, Rman reads information from the snapshot control file for backup, and the snapshot control file does not contain a new tablespace, so there is no tbs_test.dbf in the backup set
--c, after the backup is complete, the control file and the SPFile file are automatically backed up.
--d, refresh the snapshot control file
--E, so the above detection in the control file, the snapshot control file, the backup control file contains the information of the new table space. However, there is no backup because the tablespace is added after the backup is started.
--Adjust the snapshot control file location to the default path
Rman> Configure snapshot Controlfile name clear;

Oracle Snapshot Control file (snapshot)