Note_Tech

All technological notes.

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Recovery - Complete Recovery

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• Recovery - Complete Recovery
  • Restore Command
  • Restore Points

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Restore Command

• Commands to check the validity of the backups

RMAN Command	Action
RESTORE PREVIEW	reports the backups and archived redo log files uesd to restore
RESTORE VALIDATE	determines and validate backup, copies, and archived redo log to restore
RECOVER VALIDATE HEADER	Reports and validates the backups to restore for the recovery

• RESTORE PREVIEW:

  • Reports on the backups and archived redo log files that RMAN can use to restore and recover the database to the specified time. 列出需要的文件
  • RMAN queries the metadata, but does not actually read the backup files.不读取文件
  • The output from this command is in the same format as the LIST BACKUP command output.

• RESTORE VALIDATE:

  • Specifies that RMAN should decide which backup sets, data file copies, and archived redo log files need to be restored and then validate them.
  • No files are restored.
  • For files on both disk and tape, RMAN reads all blocks in the backup piece or image copy. 读取文件
  • RMAN also validates off-site backups.

• RECOVER VALIDATE HEADER:

  • Reports on and validates the backups that RMAN can use to restore files needed for recovery.
  • RMAN performs the same operations as when you specify the RESTORE PREVIEW command.
    • Additional, RMAN validates the backup file headers to determine whether the files on disk or in the media management catalog correspond to what is in the metadata in the RMAN repository. 验证文件头

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Restore Points

• restore point

  • provides a name to a point in time
  • a user-defined name associated with an SCN of the database corresponding to the time of the creation of the restore point.
  • useful for future reference, when performing point-in-time recovery or flashback operations.

• There are two types of restore points:

  • Guaranteed restore point:
    • Enforces the retention of flashback logs required for Flashback Database back to any point in time after the creation of the earliest guaranteed restore point.
    • does not age out of the control file
    • must be explicitly dropped.
  • Normal restore point:
    • A label for an SCN or time.
    • exist in a circular list
    • can be overwritten in the control file.

• Example:

-- creates a restore point that represents the present point in time.
CREATE RESTORE POINT before_mods;

-- creates a restore point representing a past SCN, 100
CREATE RESTORE POINT end_ql AS OF SCN 100;

• Normally, restore points are maintained in the database for at least as long as specified by the CONTROL_FILE_RECORD_KEEP_TIME initialization parameter.默认保留时长=cf 参数

• PRESERVE option:

  • causes the restore point to be saved until you explicitly delete it.保留恢复点直到显式删除
• Views:
  • V$RESTORE_POINT: display estore points’ name, SCN, time stamp, and other information.

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