Preface
In Oracle database management, the loss or misdeletion of data files (usually with .dbf as the extension) is a very serious situation and may lead to inaccessibility or even permanent loss of data. This article aims to provide database administrators with effective strategies and steps to handle error deletion of DBF data files in Oracle databases.
1. Confirm the situation
First, you need to determine which DBF files have been deleted by mistake, and understand which tablespace these files belong to and the scope of impact. This can be searchedDBA_DATA_FILESView to get relevant information:
SELECT * FROM DBA_DATA_FILES;
This query will display all data files and their tablespace information to which they belong, helping to identify missing data files.
2. Emergency measures
(I) Stop relevant operations immediately
Once a DBF file is found to be deleted by mistake, all writes to the tablespace should be suspended immediately to prevent overwriting of data blocks that may be used for recovery, which can reduce the risk of data loss.
(II) Check the operating system level
In some cases, if the database instance is still running and there is no space to reuse the data file, the deleted file may be restored at the operating system level. For example, on Linux systems, you can try to use the lsof command to find file descriptors that have been deleted but are still held by the process and recover data from there. This article will focus on this method.
3. Restore using backup
If no solution is found at the operating system level, you need to rely on the recent backup to restore. Here are the basic steps:
Prepare the environment: Ensure that there is enough storage space to store the restored data files, and that the recovery environment is as consistent as possible with the original production environment.
Recovery with RMAN: Oracle Recovery Manager (RMAN) is the main tool for recovering data files. Choose the appropriate recovery script depending on the recovery scenario (full recovery or incomplete recovery). For example, to restore a specific data file, you can use the following command:
RUN {
RESTORE DATAFILE '<datafile_path>';
RECOVER DATAFILE '<datafile_path>';
}where <datafile_path> is the path of the data file you want to recover.
Verify recovery results: After the recovery is completed, be sure to conduct a health check on the database to ensure that all data files are online normally, and verify data integrity through query or other means.
4. Advanced recovery options
If there is neither a backup available nor a deleted file is found at the operating system level, you can consider using more advanced techniques such as Flashback Database or Data Pump export and import methods, but it depends on your database configuration and specific needs.
5. Simulate operating system recovery
5.1 Delete data files
[oracle@database oracle]$ cd /opt/oracle/oradata/ORCLCDB [oracle@database ORCLCDB]$ rm
5.2 Try to create a table on this tablespace and find an error
SYS@ORCLCDB> create table t1(id int) tablespace users; create table t1(id int) tablespace users * ERROR at line 1: ORA-01116: error in opening database file 7 ORA-01110: data file 7: '/opt/oracle/oradata/ORCLCDB/' ORA-27041: unable to open file Linux-x86_64 Error: 2: No such file or directory Additional information: 3
5.3 Find the process ID of dbw
[oracle@database ORCLCDB]$ ps -ef|grep dbw oracle 29459 1 0 03:31 ? 00:00:05 ora_dbw0_ORCLCDB oracle 34599 33456 0 10:50 pts/2 00:00:00 grep --color=auto dbw
5.4 Find the file handle through the process number
[oracle@database ORCLCDB]$ cd /proc/29459/fd [oracle@database fd]$ ll total 0 lr-x------ 1 oracle oinstall 64 Jul 15 10:51 0 -> /dev/null l-wx------ 1 oracle oinstall 64 Jul 15 10:51 1 -> /dev/null l-wx------ 1 oracle oinstall 64 Jul 15 10:51 2 -> /dev/null lrwx------ 1 oracle oinstall 64 Jul 15 10:51 256 -> /opt/oracle/oradata/ORCLCDB/ lrwx------ 1 oracle oinstall 64 Jul 15 10:51 257 -> /opt/oracle/oradata/ORCLCDB/ lrwx------ 1 oracle oinstall 64 Jul 15 10:51 258 -> /opt/oracle/oradata/ORCLCDB/ lrwx------ 1 oracle oinstall 64 Jul 15 10:51 259 -> /opt/oracle/oradata/ORCLCDB/ lrwx------ 1 oracle oinstall 64 Jul 15 10:51 260 -> /opt/oracle/oradata/ORCLCDB/ lrwx------ 1 oracle oinstall 64 Jul 15 10:51 261 -> /opt/oracle/oradata/ORCLCDB/ lrwx------ 1 oracle oinstall 64 Jul 15 10:51 262 -> '/opt/oracle/oradata/ORCLCDB/ (deleted)' lrwx------ 1 oracle oinstall 64 Jul 15 10:51 263 -> /opt/oracle/oradata/ORCLCDB/ORCLPDB1/ 。。。。
5.5 Copy the handle file into the deleted DBF file
[oracle@database fd]$ cp /proc/29459/fd/262 /opt/oracle/oradata/ORCLCDB/
5.6 Media recovery for this DBF file
SYS@ORCLCDB> alter database datafile 7 offline; Database altered. SYS@ORCLCDB> recover datafile 7; Media recovery complete. SYS@ORCLCDB> alter database datafile 7 online; Database altered.
5.7. Try to create a table on this tablespace again successfully
SYS@ORCLCDB> create table t1(id int) tablespace users; Table created.
VI. Preventive measures
The above experiment is only applicable to scenarios where the database has not downtime. In most cases, the DBA only finds that the data file is lost after receiving a fault alarm. This method is not applicable. To avoid similar problems again in the future, the following precautions are recommended:
Perform a full backup periodically and test the recovery process.
Enable the flashback database feature to quickly recover to a certain point in time.
Implement remote disaster recovery plans for important data to improve disaster recovery capabilities.
In short, in the face of unexpected deletion of DBF data files in Oracle database, timely response, accurate judgment and reasonable use of existing resources are the key to successful recovery. I hope the above content can help database administrators effectively deal with this challenge.
The above is the detailed content of the recovery guide for Oracle's mistakenly deleting DBF data files. For more information about Oracle's mistakenly deleting DBF data, please pay attention to my other related articles!