Oracle Grid Infrastructure - reconfiguration

There are some situations we need to reconfigure the Grid Home like IP-address change/hostname changer,
fresh GI installation due to binary issue etc..
Please follow the below steps


0. Please capture the below details before you do reconfigurations
      crsctl stat res -p
      crsctl stat res -t
      cluster Name:cemutlo -n
      scan name :  srvctl confif scan
      listener port :  srvctl confif listener
      host vip names
      if you are doing it in exadata   . please do the step 3 before you do the reconfiguration


1. Run the below command to deconfig the GI from all the nodes except the last node.

 $ORACLE_HOME/crs/install/rootcrs.pl -verbose -deconfig -force

2. Run the below command in the last node ( keepdg to retain the DG configuration)
 $ORACLE_HOME\crs\install\rootcrs.pl -deconfig -force -verbose -lastnode -keepdg





3. During reconfiguration, incase if the OCR disks are not listed as candidates for OCR DG creations, we may need to delete and add the disks

    ORACLE ASM:
            we can use either Plan A or Plan B         
          
           Plan A:
                   oracleasm createdisk <label> <dev_mapper>
                   oracleasm createdisk OCR_DK1  /dev/mapper/ASM_OCR_0001
                  
          Plan B:
                 incase the above is faling with "Unable to open device "/dev/mapper/ASM_OCR_0001": Device or resource busy "
          /usr/sbin/asmtool -C -l /dev/oracleasm -n OCR_DK1 -s  /dev/mapper/ASM_OCR_0001 -a force=yes

          Post task:
                   oracleasm scandisks
                   oracleasm listdisks
     AFD:
            ( BS = block size) and count= 1000 * BS = size of the disk
     
              dd if=/dev/zero of=/dev/mapper/ASM_REG_OCR_0001 bs=1M count=1000
        Post task:
       asmcmd afd_scan
       asmcmd afd_lsdsk
    Exadata:
             delete 3 disks from a DG from different cell to make them as a candidate for the OCR DG ( this step need to be done before the deconfigruation run)


4. Cleanup the gpnp files from all the nodes
  find <GRID_HOME>/gpnp/* -type f -exec rm -rf {} \;




5. run config.sh
 cd $ORACLE_HOME/crs/config
 ./config.sh

 feed the below values
    => cluster_name, scan name, port & Disable GNS if it is not used.
    => ensure all the host and VIPs are fetched automatically, if not, please add them manually.
    => Storage for OCR: create new DG and choose the disks candidates.