A block corruption in a database is a rare and unwanted situation. However, for testing corruption recovery scenario a DBA needs to have a actual corruption at the block level.
I have written a wrapper script that can be used to introduce artificial block corruption in a Oracle Database for the purpose of testing block media recovery scenarios.
Few words of Caution:
Do Not execute the script on a Production Environment
Ensure that you have valid database backup available before simulating block corruption
#!/bin/sh
######################################################################
# Script : manual_block_corrupt.sh
# Author : Abu Fazal Mohammed Abbas
# Version : 1.2
# Description : Script to induce artificial block corruption
######################################################################
clear
# Check existance of ORATAB
if [ -f /etc/oratab ] ; then
OTAB="/etc/oratab"
elif [ -f /var/opt/oracle/oratab ] ; then
OTAB="/var/opt/oracle/oratab"
else
echo "Could not locate ORATAB. Terminating program"
exit 1
fi
# Prompt the list of Running databases
echo "Script to introduce artificial database block corruption"
echo "Developed By : Abu Fazal Abbas"
echo
echo "Select database from the list"
echo `ps -ef | grep pmon | grep -v ASM | grep -v grep | awk '{print $NF}' | cut -c 10-`
echo
echo -e "Enter your choice:\c "
read dbname
# Set Oracle Database environment
set_env()
{
ORACLE_SID=$dbname ; export ORACLE_SID
ORAENV_ASK=1; export ORAENV_ASK
ORACLE_HOME=`cat $OTAB | grep -v "^#" | grep "^[A-Za-z,+]" | grep -w $ORACLE_SID | awk -F: '{print $2}'`
export ORACLE_HOME
PATH=${ORACLE_HOME}/bin:${PATH}; export PATH
if [ "x$LD_LIBRARY_PATH" != "x" ]
then
LD_LIBRARY_PATH=${ORACLE_HOME}/lib:${ORACLE_HOME}/lib64:${LD_LIBRARY_PATH}; export LD_LIBRARY_PATH
fi
}
# Unset Oracle Database environment
unset_env()
{
PATH=`echo $PATH | sed "s;:$ORACLE_HOME/bin;;g"`; export PATH
if [ "x$LD_LIBRARY_PATH" != "x" ]
then
LD_LIBRARY_PATH=`echo $LD_LIBRARY_PATH | sed "s;:$ORACLE_HOME/lib;;g"`; export LD_LIBRARY_PATH
LD_LIBRARY_PATH=`echo $LD_LIBRARY_PATH | sed "s;:$ORACLE_HOME/lib64;;g"`; export LD_LIBRARY_PATH
fi
}
# Corrupt Block module
corrupt_database()
{
echo
echo -e "Introduce artificial corruption[Y/N]: \c"
read opt
case $opt in
y|Y)
echo
echo "Corrupting block $header_b, `expr $header_b + 1`, `expr $header_b + 2` in '$cdf'"
dd if=/dev/zero of=$cdf bs=$bsize conv=notrunc seek=$header_b count=3
echo "Validating Block corruption from database. Please wait"
$ORACLE_HOME/bin/rman << EOF
connect target /
backup validate datafile '$cdf';
exit
EOF
$ORACLE_HOME/bin/sqlplus -S << EOF > /tmp/chk_bc.log
/ as sysdba
select * from v\$database_block_corruption;
exit;
EOF
cat /tmp/chk_bc.log
rm -f /tmp/chk_bc.log
;;
n|N)
echo
echo "You have decided, not to proceed. Terminating Program"
unset_env
exit 1
;;
*)
echo
echo "Invalid Option. Terminating Program"
unset_env
exit 1
;;
esac
}
# Main Program
if [ "`ps -ef | grep pmon | grep -v ASM | grep -v grep | awk '{print $NF}' | cut -c 10- | grep -w $dbname`" = "" ]; then
echo "Invalid Database Name.. Terminating Program"
exit 1
else
echo "1. Corrupt a Datafile"
echo "2. Corrupt a Table"
echo -e "Select your option: \c"
read c_choice
if [ $c_choice -eq 1 ]; then
set_env
echo
echo "Scanning datafiles for $ORACLE_SID. Please wait..."
echo
df_sql="select name from v\$datafile;"
df_list=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feedback off head off
$df_sql
exit
EOF`
echo "Datafile"
echo "------------------------------------------------------------------"
for df in $df_list
do
echo $df
done
echo
echo -e "Select the datafile for artificial corruption: \c"
read cdf
if [ "`echo $df_list | grep -w $cdf`" = "" ]; then
echo "Invalid datafile selection. Terminating Program..."
unset_env
exit 1
else
echo
echo "Scanning datafile segments to find a header block"
header_sql="select header_block from dba_segments where header_file=(select file# from v\$datafile where name='$cdf') and rownum <2;"
header_b=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$header_sql
exit
EOF`
header_b=`echo $header_b | tr -d " "`
if [ "$header_b" = "" ]; then
echo
echo "Datafile '$cdf' has no segments for corruption. Terminating program..."
unset_env
exit 1
else
echo
echo "Retrieving datafile block size for '$cdf'"
bsize_sql="select block_size from v\$datafile where name='$cdf';"
bsize=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$bsize_sql
exit
EOF`
bsize=`echo $bsize | tr -d " "`
echo
echo "Final Selection:-"
echo "Datafile: $cdf"
echo "Block Size: $bsize"
echo "Blocks to be corrupted: $header_b, `expr $header_b + 1`, `expr $header_b + 2`"
echo
corrupt_database
fi
unset_env
fi
elif [ $c_choice -eq 2 ]; then
echo
echo -e "Enter Schema Name: \c"
read s_name
echo -e "Enter Table Name: \c"
read t_name
set_env
chk_table_sql="select table_name from dba_tables where owner=upper('$s_name') and table_name=upper('$t_name');"
chk_tabseq_sql="select count(*) from dba_segments where segment_name=upper('$t_name') and owner=upper('$s_name');"
chk_table=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$chk_table_sql
exit
EOF`
chk_tabseq=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$chk_tabseq_sql
exit
EOF`
chk_tabseq=`echo $chk_tabseq | tr -d " "`
if [ "$chk_table" == "" ]; then
echo "Specified table doesn't exist. Terminating program"
unset_env
exit
elif [ $chk_tabseq -eq 0 ]; then
echo "Table segment doesn't exist for table '$s_name.$t_name'. Terminating program"
unset_env
exit 1
else
t_header_b_sql="select header_block from dba_segments where SEGMENT_NAME=upper('$t_name') and owner=upper('$s_name');"
t_dbf_sql="select name from v\$datafile where file#=(select header_file from dba_segments where SEGMENT_NAME=upper('$t_name') and owner=upper('$s_name'));"
echo
echo "Retrieving Table Header..."
header_b=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$t_header_b_sql
exit
EOF`
echo
echo "Retrieving datafile details..."
cdf=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$t_dbf_sql
exit
EOF`
header_b=`echo $header_b | tr -d " "`
cdf=`echo $cdf | tr -d " "`
g_bsize_sql="select block_size from v\$datafile where name='$cdf';"
bsize=`$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
set feed off head off
$g_bsize_sql
exit
EOF`
bsize=`echo $bsize | tr -d " "`
echo
echo "Final Selection:-"
echo "Schema: $s_name"
echo "Table Name: $t_name"
echo "Datafile: $cdf"
echo "Block Size: $bsize"
echo "Blocks to be corrupted: $header_b, `expr $header_b + 1`, `expr $header_b + 2`"
echo
corrupt_database
echo
echo "Crosschecking table access"
$ORACLE_HOME/bin/sqlplus -S << EOF
/ as sysdba
select count(*) from $s_name.$t_name;
exit
EOF
fi
else
echo "Invalid Choice. Terminating"
exit 1
fi
fi