In the last article, we performed downgrade of Oracle RAC Database from 12c to 11gR2In this article, we are going to downgrade Oracle Grid Infrastructure from 12c (12.1.0.2) to 11gR2 (11.2.0.4) which contains two nodes ( node 1 & node 2).

Before doing CRS downgrade we need to take backup of following files :

  • Take tar backup of $ORA_CRS_HOME from both nodes.
  • Take tar backup of ORAINVENTORY from both nodes.
  • Take voting disk backup from one node. In 11gR2, your voting disk data is automatically backed up in the OCR
  • Take a backup of init.d folder in /etc folder on both nodes.

Firstly, perform prechecks on existing Grid Home

To begin the downgrade run the rootcrs.sh with downgrade option on all but the OCR-node. In this case, the node1 is the OCR-node and downgrade first run on node2. It means we need to execute the following command as root from non-master node with 12.1.0.2 cluster home.

How to Find Master Node.

Since this is a two node RAC the downgrade command is run with a lastnode option on node1 (OCR-node). This will remove the GI management repository, downgrade the OCR

Before starting the cluster with 11.2 update the inventory by setting crs=true for 11.2 GI home. At this point 12.1 GI home will have crs=true.

Run the following to update the inventory

Verify the inventory update

Start the CRS on all nodes.

This concludes the steps to successfully downgrading GI from 12.1.0.2 to 11.2.0.4.

Thank you for giving your valuable time to read the above information.

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Comments

  1. ANAND JANAKIRAMAN

    One more way to find the lastnode.

    cd /opt/oracle/product/11.2.0.4/grid/cdata

    pwd

    ls -lrt
    total 266508

    -rw——-. 1 root root 130663 Sep 6 11:56 ocr11.2.0.3.0 – check for similar file on both new grid home.

    with this we can conclude this is the last node.

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