Oracle RAC removal steps

1. Stop and remove all ASM and RAC instances with SRVCTL command

srvctl disable instance -d <DB_NAME> -i <INSTANCE_NAME>
srvctl disable asm -n <HOST_NAME>

srvctl stop instance -d <DB_NAME> -i <INSTANCE_NAME>
srvctl remove instance -d <DB_NAME> -i <INSTANCE_NAME>

srvctl stop asm -n <HOST_NAME>
srvctl remove asm -n <HOST_NAME>

2. Remove the following files/folders from /etc: oracle, orainst, oratab, ORCLcluster

sudo rm -rf /etc/oracle /etc/orainst /etc/oratab /etc/ORCLcluster 

sudo rm -rf /etc/init.d/init.crsd /etc/init.d/init.crs /etc/init.d/init.cssd /etc/init.d/init.evmd 

4. Remove soft links to /etc/init.d/init.crs from the /etc/rc2.d, /etc/rc3.d, /etc/rc5.d folders

sudo rm -rf /etc/rc2.d/K96init.crs /etc/rc2.d/S96init.crs /etc/rc3.d/K96init.crs /etc/rc3.d/S96init.crs /etc/rc5.d/K96init.crs /etc/rc5.d/S96init.crs 

5. From the /etc/inittab file remove last three lines starting with h1, h2, h3

6. Restart init

telinit q 

7. Remove the contents of /tmp folder

sudo rm -rf /tmp/*

8. From the /usr/local/bin remove dbhome, oraenv, coraenv files

sudo rm -rf /usr/local/bin/dbhome /usr/local/bin/oraenv /usr/local/bin/coraenv

9. Remove /var/tmp/.oracle folder

sudo rm -rf /var/tmp/.oracle

10. From the /ORA/dbs01/oracle folder remove all subfolders except home

sudo rm -rf /ORA/dbs01/oracle/admin /ORA/dbs01/oracle/product /ORA/dbs01/oracle/oraInventory

Prepare re-installation

11. unset variables

unset ORACLE_HOME;
unset TNS_ADMIN;

12. shutdown virtual interface

/sbin/ifconfig eth0:1 down;

13. clean contents of ASM disks

for letter in b4 c d e f g h j4 k l m n o p q; do dd if=/dev/zero of=/dev/sd$letter bs=1024 count=1000; done;

14. clean contents of ASM disks

for letter in 1 2 3; do dd if=/dev/zero of=/dev/raw/raw$letter bs=1024 count=1000; done;

15. reload QLA driver

/sbin/rmmod qla2300; /sbin/modprobe qla2300;

16. change permissions

chown oracle:ci /dev/raw/raw1 /dev/raw/raw2 /dev/raw/raw3;

17. ASM reconfiguation (primary node only)

/etc/init.d/oracleasm configure (answers: oracle; ci; y; y)

18. Recreate ASM disks (primary node only)

/etc/init.d/oracleasm createdisk STOR15_1 /dev/sdb4;
/etc/init.d/oracleasm createdisk STOR15_2 /dev/sdc;
/etc/init.d/oracleasm createdisk STOR15_3 /dev/sdd;
/etc/init.d/oracleasm createdisk STOR15_4 /dev/sde;
/etc/init.d/oracleasm createdisk STOR15_5 /dev/sdf;
/etc/init.d/oracleasm createdisk STOR15_6 /dev/sdg;
/etc/init.d/oracleasm createdisk STOR15_7 /dev/sdh;

/etc/init.d/oracleasm createdisk STOR16_1 /dev/sdj4;
/etc/init.d/oracleasm createdisk STOR16_2 /dev/sdk;
/etc/init.d/oracleasm createdisk STOR16_3 /dev/sdl;
/etc/init.d/oracleasm createdisk STOR16_4 /dev/sdm;
/etc/init.d/oracleasm createdisk STOR16_5 /dev/sdn;
/etc/init.d/oracleasm createdisk STOR16_6 /dev/sdo;
/etc/init.d/oracleasm createdisk STOR16_7 /dev/sdp;
/etc/init.d/oracleasm createdisk STOR16_8 /dev/sdq;

19. Synchronize ASM (other nodes)

/etc/init.d/oracleasm enable;
/etc/init.d/oracleasm scandisks;