How to Remove ASM Diskgroups and ASM Instance

This document will describe how to remove an ASM instance from a RAC node. It will also describe the entire process for removing ASM, removing ASM Diskgroups, and reinstalling ASM Instance.
This process is used to clean up a failed ASM install and wipe all ASM Instance/Diskgroups to prepare systems for a new ASM installation.
How to Remove ASM Instance and DiskGroups
  1. Check ASM status on RAC Nodes
    • Login via oracle and run showcrs  to view status.
  2. Stop ASM instance on each node:
    • srvctl stop asm -n node (where node is node name, ie srv0dbxd11)
  3. Login to node 2 and 3 and run . oraenv and source +ASMx where X=instance number, ie. +ASM2 for node2.
  4. Go to sqlplus with sqlplus sys as sysdba and do the following on node 2 & 3 first:
    • SQL> Alter diskgroup all dismount;
  5. Back on Node1, run sqlplus again and list all ASM Diskgroups with this command:
    • SQL> select name,total_mb from v$asm_diskgroup;
    • NAME                             TOTAL_MB
      —————————— ———-
      DWAK_BACKUP_01                      40954
      DWAK_DATA_01                       225252
  6. To remove these ASM Diskgroups, complete the following command (Make sure you want to remove these)
    • SQL> drop diskgroup dwak_data_01 including contents;
    • Should see: Dropped dwakdb_data_01 successfully
    • Run drop command again for any other ASM diskgroups to remove.
  7. Next while logged in as Oracle on Node 1, remove all ASM instances
    • srvctl remove asm -n nodeX (where nodeX=srv0dbxd13 for example)
    • run for each node in RAC cluster.
  8. Next edit the /etc/oratab file on all nodes in RAC Cluster and remove the following line:
    • +ASM1:/u00/app/oracle/product/10.2.0/ASM:N  (remove this on all nodes)
  9. As root, verify all Oracle ASM disks are listed properly and run scandisks
    • [[email protected] init.d]# ./oracleasm listdisks
    • [[email protected] init.d]# ./oracleasm scandisks
      Scanning system for ASM disks:                             [  OK  ]
    • then run ./oracleasm restart to restart ASM
  10. Once everything is okay, you can reinstall ASM Instance.
    • Login to node 1 with VNC.
    • Run xhost +
    • su – oracle
    • . oraenv
    • +ASM1 and enter /u00/app/oracle/product/10.2.0/ASM for ORACLE_HOME
    • cd $ORACLE_HOME/bin and run ./dbca
    • choose Install ASM
    • Follow How to Install Oracle 10gR4 ASM Instance  guide.