Skip to main content

How to Corrupt Oracle Database Block Manually


<<Back to Oracle ASM Main Page

Corrupting Oracle Database Block Intensely

Note:- The post is only intended for educational and knowledge purpose, must not be tried in Live (prod as well as non-prod) database.

CASE1: When ASM is Used
Let's say I want to corrupt  Block#132 of  datafile# 9 stored in ASM File#256 and ASM DG#4
I already know
DB_BLOCK_SIZE  is 8k and ASM AU_SIZE => 1M for the tablespace holding this block. Check out  Trace Down Your Data from Database to Disk to find out the above details. That's said let's proceed
1M of AU can hold 128 DB Blocks of 8K size and therefore with simple math calculation we can find that the block number 132 is the 4th block in 2nd ASM Extent.
So Let us find the Disk holding this block physically and corrupt it using dd.

Login to ASM Instance and run below query to find the AU distribution across the disk.
SQL> select XNUM_KFFXP,
DISK_KFFXP,
AU_KFFXP
from X$KFFXP
where NUMBER_KFFXP=256
AND GROUP_KFFXP=4
AND XNUM_KFFXP<=2;
XNUM_KFFXP    DISK_KFFXP   AU_KFFXP
---------- ----------                            ----------
         0                    0                                 61
         0                    1                                 61
         1                    1                                 62<= 2nd Extent (Primary AU)
         1                    0                                 62<=2nd Extent (Secondary AU)
         2                    0                                 63
         2                    1                                 63
6 rows selected.
So from the output we can see that the data is physically stored on Disk#0 (Secondary Copy) and Disk#1 (Primary Copy).

Lets Find these Disk on OS
SQL>  select DISK_NUMBER, NAME from V$ASM_DISK where DISK_NUMBER in (0,1) and GROUP_NUMBER=4;
DISK_NUMBER NAME
----------- ------------------------------
          0 DATA_TEST
          1 DATA_TEST1
$ asmcmd afd_lsdsk |grep TEST
DATA_TEST                   ENABLED   /dev/xvde
DATA_TEST1                  ENABLED   /dev/xvdf

Lets Corrupt It.
#dd if=corrupt of=/dev/xvde  bs=8k  count=1 seek=7940
Verify the Corruption from ASM Instance
SQL> alter diskgroup TEST_DATA scrub file '+TEST_DATA/WDTESTDBA/DATAFILE/TRACE_DATA.256.984068463';
Diskgroup altered.

Examine the ASM Alert Log
SQL> alter diskgroup TEST_DATA scrub file '+TEST_DATA/WDTESTDBA/DATAFILE/TRACE_DATA.256.984068463'
Starting background process SCRB
2018-08-16T12:33:10.586097+02:00
SCRB started with pid=30, OS id=25618
2018-08-16T12:33:10.587580+02:00
SUCCESS: alter diskgroup TEST_DATA scrub file '+TEST_DATA/WDTESTDBA/DATAFILE/TRACE_DATA.256.984068463'
2018-08-16T12:33:23.795765+02:00
Starting background process ASMB
2018-08-16T12:33:23.808254+02:00
ASMB started with pid=33, OS id=25728
2018-08-16T12:33:23.871583+02:00
NOTE: ASMB0 registering with ASM instance as Standard client 0xffffffffffffffff (reg:3966494159) (new connection)
2018-08-16T12:33:23.995566+02:00
NOTE: Standard client +ASM:+ASM:ASM registered, osid 25730, mbr 0x0, asmb 25728 (reg:3966494159)
2018-08-16T12:33:23.995884+02:00
NOTE: ASMB0 (25728) connected to ASM instance +ASM, osid: 25730 (Flex mode; client id 0xffffffffffffffff)
2018-08-16T12:33:24.032471+02:00
NOTE: Corrupted block 132 found in file +TEST_DATA/WDTESTDBA/DATAFILE/TRACE_DATA.256.984068463
2018-08-16T12:33:24.834625+02:00

CASE2: When File System is Used.
Create a Tablespace test_corruption
SQL> create tablespace test_corruption datafile '/u01/dbatst1/c1_test01.dbf' size 20m;Tablespace created.
Create a table test_corruption in tablespace test_corruption
SQL> create table test_corruption(name varchar(20)) tablespace test_corruption ;Table created.
Inset some data in table test_corruption
SQL> insert into test_corruption values ('TESTING');
SQL> insert into test_corruption values ('TESTING');
SQL> insert into test_corruption values ('TESTING');
SQL> insert into test_corruption values ('TESTING');
SQL> commit;
Commit complete.
Find the header Blok of the table 
SQL> SELECT header_block FROM dba_segments WHERE segment_name='TEST_CORRUPTION';

HEADER_BLOCK
------------
         130
Do the Corruption in Data Block (Skip the header Block) 
$ dd of=/u01/dbatst1/c1_test01.dbf bs=8192 conv=notrunc seek=1030 << EOF
> CORRUPT corrupt CORRUPT corrupt CORRUPT corrupt CORRUPT corrupt CORRUPT CORRUPT CORRUPT CORRUPT corrupt corrupt
> EOF
0+1 records in
0+1 records out
113 bytes (113 B) copied, 0.000206179 s, 548 kB/s
SQL> alter system switch logfile;
System altered.
SQL> alter system checkpoint;
System altered.
Validate the Corruption
$ rman target /
RMAN> validate tablespace test_corruption ;
Starting validate at 16-AUG-18
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=37 device type=DISK
channel ORA_DISK_1: starting validation of datafile
channel ORA_DISK_1: specifying datafile(s) for validation
input datafile file number=00011 name=/u01/dbatst1/c1_test01.dbf
channel ORA_DISK_1: validation complete, elapsed time: 00:00:01
List of Datafiles
=================
File Status Marked Corrupt Empty Blocks Blocks Examined High SCN
---- ------ -------------- ------------ --------------- ----------
11   FAILED 0              2424         2560            2100178
  File Name: /u01/dbatst1/c1_test01.dbf
  Block Type Blocks Failing Blocks Processed
  ---------- -------------- ----------------
  Data       0              5
  Index      0              0
  Other      1              131
validate found one or more corrupt blocks
See trace file /u01/dbatst1/diag/rdbms/wdtestdba/WDTESTDBA/trace/WDTESTDBA_ora_20899.trc for details
Finished validate at 16-AUG-18
SQL> select * from v$database_block_corruption;
     FILE#     BLOCK#     BLOCKS CORRUPTION_CHANGE# CORRUPTIO     CON_ID
---------- ---------- ---------- ------------------ --------- ----------
        11       1030          1                  0 CORRUPT            1


Comments

Post a Comment

Popular posts from this blog

How to Power On/off Oracle Exadata Machine

<<Back to Exadata Main Page How to Power On/off Oracle Exadata Machine Oracle Exadata machines can be powered on/off either by pressing the power button on front of the server or by logging in to the ILOM interface. Powering on servers using  button on front of the server The power on sequence is as follows. 1. Start Rack, including switches  Note:- Ensure the switches have had power applied for a few minutes to complete power on  configuration before starting Exadata Storage Servers 2.Start Exadata Storage Servers  Note:- Ensure all Exadata Storage Servers complete the boot process before starting the   database servers 3. Start Database Servers Powering On Servers Remotely using ILOM The ILOM can be accessed using the Web console, the command-line interface (CLI), IPMI, or SNMP. For example, to apply power to server dm01cel01 using IPMI, where dm01cel01-ilom is the host name of the ILOM for the server to be powered on, run the
Post a Comment
Read more

How to Find VIP of an Oracle RAC Cluster

<<Back to Oracle RAC Main Page How to Find Out VIP of an Oracle RAC Cluster Login clusterware owner (oracle) and execute the below command to find out the VIP hostname used in Oracle RAC $ olsnodes -i node1     node1-vip node2     node2-vip OR $ srvctl config nodeapps -viponly Network 1 exists Subnet IPv4: 10.0.0.0/255.255.0.0/bondeth0, static Subnet IPv6: Ping Targets: Network is enabled Network is individually enabled on nodes: Network is individually disabled on nodes: VIP exists: network number 1, hosting node node1 VIP Name: node1-vip VIP IPv4 Address: 10.0.0.1 VIP IPv6 Address: VIP is enabled. VIP is individually enabled on nodes: VIP is individually disabled on nodes: VIP exists: network number 1, hosting node node2 VIP Name: node2-vip VIP IPv4 Address: 10.0.0.2 VIP IPv6 Address: VIP is enabled. VIP is individually enabled on nodes: VIP is individually disabled on nodes:
1 comment
Read more

ORA-28374: typed master key not found in wallet

<<Back to Oracle DB Security Main Page ORA-46665: master keys not activated for all PDBs during REKEY SQL> ADMINISTER KEY MANAGEMENT SET KEY FORCE KEYSTORE IDENTIFIED BY xxxx WITH BACKUP CONTAINER = ALL ; ADMINISTER KEY MANAGEMENT SET KEY FORCE KEYSTORE IDENTIFIED BY xxxx WITH BACKUP CONTAINER = ALL * ERROR at line 1: ORA-46665: master keys not activated for all PDBs during REKEY I found following in the trace file REKEY: Create Key in PDB 3 resulted in error 46658 *** 2019-02-06T15:27:04.667485+01:00 (CDB$ROOT(1)) REKEY: Activation of Key AdnU5OzNP08Qv1mIyXhP/64AAAAAAAAAAAAAAAAAAAAAAAAAAAAA in PDB 3 resulted in error 28374 REKEY: Keystore needs to be restored from the REKEY backup.Aborting REKEY! Cause: All this hassle started because I accidently deleted the wallet and all wallet backup files too and also forgot the keystore password. There was no way to restore the wallet back. Fortunately in my case the PDB which had encrypted data was supposed to be deco
7 comments
Read more

ORA-16905: The member was not enabled yet

<<Back to Oracle DataGuard Main Page ORA-16905 Physical Standby Database is disabled DGMGRL> show configuration; Configuration - DG_ORCL1P   Protection Mode: MaxPerformance   Members:   ORCL1PP - Primary database     ORCL1PS - Physical standby database (disabled)       ORA-16905: The member was not enabled yet. Fast-Start Failover:  Disabled Configuration Status: SUCCESS   (status updated 58 seconds ago) DGMGRL> DGMGRL> enable database 'ORCL1PS'; Enabled. DGMGRL>  show configuration; Configuration - DG_ORCL1P   Protection Mode: MaxPerformance   Members:   ORCL1PP - Primary database     ORCL1PS - Physical standby database Fast-Start Failover:  Disabled Configuration Status: SUCCESS   (status updated 38 seconds ago)
Post a Comment
Read more

How to Switch Log File from All Instances in RAC

<<Back to Oracle RAC Main Page Switch The Log File of All Instances in Oracle RAC. In many cases you need to switch the logfile of the database. You can switch logfile using alter system switch logfile command but if you want to switch the logfile from all the instances you need to execute the command on all the instances individually and therefore you must login on all the instances. You can avoid this and switch logfile of all instances by just running the below command from any of the instance in RAC database SQL> ALTER SYSTEM SWITCH ALL LOGFILE;   System altered.
Post a Comment
Read more

ORA-65104: operation not allowed on an inactive pluggable database alter pluggable database open

<<Back to DB Administration Main Page ORA-65104: operation not allowed on an inactive pluggable database SQL> alter pluggable database TEST_CLON open; alter pluggable database TEST_CLON open * ERROR at line 1: ORA-65104: operation not allowed on an inactive pluggable database Cause The pluggable database status was UNUSABLE. It was still being created or there was an error during the create operation. A PDB can only be opened if it is successfully created and its status is marked as NEW in cdb_pdbs.status column SQL> select PDB_NAME,STATUS from cdb_pdbs; PDB_NAME             STATUS -------------------- --------------------------- PDB$SEED             NORMAL TEST_CLON            UNUSABLE Solution:  Drop the PDB and create it again. Related Posts How to Clone Oracle PDB (Pluggable Database) with in the Same Container
Post a Comment
Read more

ORA-46630: keystore cannot be created at the specified location

<<Back to DB Administration Main Page ORA-46630: keystore cannot be created at the specified location CDB011> ADMINISTER KEY MANAGEMENT CREATE KEYSTORE '+DATAC4/CDB01/wallet/' IDENTIFIED BY "xxxxxxx"; ADMINISTER KEY MANAGEMENT CREATE KEYSTORE '+DATAC4/CDB01/wallet/' IDENTIFIED BY "EncTest123" * ERROR at line 1: ORA-46630: keystore cannot be created at the specified location Cause  Creating a keystore at a location where there is already a keystore exists Solution To solve the problem, use a different location to create a keystore (use ENCRYPTION_WALLET_LOCATION in sqlnet.ora file to specify the keystore location), or move this ewallet.p12 file to some other location. Note: Oracle does not recommend deleting keystore file (ewallet.p12) that belongs to a database. If you have multiple keystores, you can choose to merge them rather than deleting either of them.
Post a Comment
Read more

Starting RMAN and connecting to Database

  <<Back to Oracle Backup & Recovery Main Page Starting RMAN and connecting to Database Starting RMAN and connecting to Database To start RMAN you need to set the environment and type rman and press enter. You can connect to database either using connect command or using command line option. using command line option localhost:$ export ORACLE_HOME=/ora_app/product/18c/dbd2 localhost:$ export PATH=$ORACLE_HOME/bin:$PATH localhost:$ export ORACLE_SID=ORCL1P localhost:$ rman target / Recovery Manager: Release 18.0.0.0.0 - Production on Sun Apr 4 08:11:01 2021 Version 18.11.0.0.0 Copyright (c) 1982, 2018, Oracle and/or its affiliates.  All rights reserved. connected to target database: ORCL1P (DBID=4215484517) RMAN> using connect option localhost:$ rman RMAN> connect target sys@ORCL1P  target database Password:******** connected to target database: ORCL1P (DBID=4215484517) NOTE: To use connect command you need to ensure that  you have proper TNS sentry for database (ORCL
Post a Comment
Read more

How to Attach to a Datapump Job and Check Status of Export or Import

<<Back to Oracle DATAPUMP Main Page How to check the progress of  export or import Jobs You can attach to the export/import  job using ATTACH parameter of oracle datapump utility. Once you are attached to the job you check its status by typing STATUS command. Let us see how Step1>  Find the Export/Import Job Name You can find the datapump job information from  DBA_DATAPUMP_JOBS or  USER_DATAPUMP_JOBS view. SQL> SELECT OWNER_NAME,JOB_NAME,OPERATION,JOB_MODE,STATE from DBA_DATAPUMP_JOBS; OWNER_NAME JOB_NAME                       OPERATION            JOB_MODE   STATE ---------- ------------------------------ -------------------- ---------- ---------- SYSTEM     SYS_EXPORT_FULL_02             EXPORT               FULL       EXECUTING OR You can also find the job name for export/import in logfile in beginning itself. Step2>Attach to the Job and check status One you get the Export/Import Job Name attach the job and check its status. You can attach or det
7 comments
Read more

ORA-15040: diskgroup is incomplete

<<Back to Oracle ASM Main Page ORA-15040: diskgroup is incomplete SQL> startup ORA-00099: warning: no parameter file specified for ASM instance ASM instance started Total System Global Area 1140850688 bytes Fixed Size                  8629704 bytes Variable Size            1107055160 bytes ASM Cache                  25165824 bytes ORA-15110: no diskgroups mounted Reason: The reason of this error is simply the ASM is not able to find the some or all the disks. Solution: Investigate and make all the disks available to ASM to mount the disk group. Make sure the disks has proper permissions. If you are using AFD check following services are online oracleacfs oracleadvm oracleoks  oracleafd   Source of Problem : Issue started after restart of the server After restarting the server when I tried to start the ASM instance its started throwing error.  ORA-15110: no diskgroups mounted Investigation in my Case Step1> ASM Logfile Scanning  Looked i
2 comments
Read more