Post upgrade of 3 Node Search Head Cluster from vesrion 8.2.7 ,one SHC Kvstore status as DOWN

[rbal_splunk]

The env was on 8.2.7.
 the environment has 3 Node Search Head Cluster.
Nodes upgraded from version 8.2.7 to  9.0.2.
Post upgrade for one  SHC member the kvstore status was  DOWN.

[rbal_splunk]

The mongod.log, it is failed to recover because of OplogStartMissing, which is a known issue https://jira.mongodb.org/browse/SERVER-40954

Error:

2022-11-29T05:01:57.080Z I REPL [rsBackgroundSync] Starting rollback due to OplogStartMissing: Our last op time fetched: { ts: Timestamp(1669697961, 2), t: 79 }. source's GTE: { ts: Timestamp(1669698089, 2), t: 80 } hashes: (6527934590833943207/-6009016642415496648)

2022-11-29T05:01:57.102Z F ROLLBACK [rsBackgroundSync] RecoverToStableTimestamp failed. :: caused by :: UnrecoverableRollbackError: No stable timestamp available to recover to. You must downgrade the binary version to v3.6 to allow rollback to finish. You may upgrade to v4.0 again after the rollback completes. Initial data timestamp: Timestamp(1669697961, 2), Stable timestamp: Timestamp(0, 0)

To resolve the issue

# splunk stop
# splunk clean kvstore --local
# splunk start

Once the KVStore is up, it was on 4.0 . Manually upgraded kvstore to  4.2 as per "Upgrade KV store server to version 4.2" and documentation https://docs.splunk.com/Documentation/Splunk/9.0.2/Admin/MigrateKVstore