Note_Tech

All technological notes.

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Recovery - Complete Recovery: NOARCHIVELOG Mode

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• Recovery - Complete Recovery: NOARCHIVELOG Mode
  • NOARCHIVELOG Mode
  • Using Incremental Backups with NOREDO option

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NOARCHIVELOG Mode

• Scenario to restore datafile

  • NOARCHIVELOG mode + any data file is lost

• Solution:

  • requires complete restoration of the database, including control files and all data files.
  • recovery is possible only up to the time of the last backup.
  • users must reenter all changes made since that backup.

• Steps:

  1. Shut down the instance if it is not already down.
  2. Restore the entire database, including all data and control files from a backup.
  3. Start the instance and open the database (CDB and all PDBs).
  4. Inform users that they must reenter all changes that were made since the last backup.

• In NoArchiveLog mode, when the database is recovery to a specific time, all CDB and PDBs are bought back to this point of time. 整体恢复, 不存在个别 pdb 能恢复到不同的时间点.

• Example:

-- connect
rman target /

-- Restore Control Files
STARTUP FORCE NOMOUNT;
RESTORE CONTROLFILE;

-- restore and recover database
ALTER DATABASE MOUNT;
RESTORE DATABASE;
RECOVER DATABASE;

-- Start the Instance and Open the Database (CDB and All PDBs):
SQL 'ALTER PLUGGABLE DATABASE ALL OPEN';

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Using Incremental Backups with NOREDO option

• Scenario

  • NOARCHIVELOG mode + any data file is lost + incremental backup strategy

• Solution:

  • RMAN uses level 0 and level 1 backups to restore and recover the database.
  • RMAN restores the most recent level 0 backup and then RMAN recovery applies the incremental backups.

• Prerequisites:

  • The incremental backups must be consistent backups.

• NOREDO option:

  • If not specifying the NOREDO option, RMAN searches for the online redo log files after applying the incremental backups. 不使用NOREDO时, 自动搜索在线档
  • If the online redo log files are not available, RMAN issues an error message.

• RECOVER DATABASE command **without the NOREDO option:**

  • when the current online redo log files contain all changes since the last incremental backup. 当前 redo 包含自上次递增备份所有改变
  • the changes will be applied.

• RECOVER DATABASE command + NOREDO option:

  • When the online redo log files are lost or if the redo cannot be applied to the incremental backups. 当前 redo 不适用

• Example:

-- restore cf
STARTUP FORCE NOMOUNT;
RESTORE CONTROLFILE;

-- resotre df
ALTER DATABASE MOUNT;
RESTORE DATABASE;

-- recover noredo
RECOVER DATABASE NOREDO;
ALTER DATABASE OPEN RESETLOGS;

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