Datastax Cassandra Administrator Certification Questions and Answer (Pratice Questions and Dumps)

Question-: You are trying to repair a table using nodetool repair command, but you have found that repair is not executed on that table. What could be the possible reason?
A. Because NodeSync is already enabled on the table
B. Repairing disable on that table
C. The node which is hosting the table is down.
D. This table was already repaired 6 hours before.

Answer: A
Exp: Whenever on the table if NodeSync is enabled then repair operation would be skipped for that table. Even you can enable NodeSync for entire keyspace as well. Hence running repair command for an individual table would be rejected when NodeSync is enabled.



Question-: Which of the following is/are correct for repairing table on a particular node?
A. You should run when node was disconnected from the cluster for some time.
B. You should run repair command at least once before gc_grace_second expire
C. You have to make sure that your repair can finish before gc_grace_second window expire
D. You should run repair command when node is under high utilization.


Answer: A, B, C
Exp: Repair a good option for bringing data in sync on all the nodes in the cluster. But you have to be careful when you should run it and when it should get completed. So, whenever you run nodetool repair command you have to make sure that it get completed before the gc_grace_second window expire. And you also have to make sure that it should run at least once for every gc_grace_second. If cluster is under heavy utilization then you should avoid firing the nodetool repair command. Because repair command is a heavy operation and creating a Merkle tree itself is an heavy operation for a node.



Question-: Please map the following options for the Nodetool repair command.

A. - -par
B. - -pr
C. - - st
D. - - local

1. Parallel repair
2. Repairs only the primary token range
3. Access Mostly Uused Products by 50000+ Subscribers
4. Apply repairs only in the local datacenter.


Answer: A-1, B-2, C-3, D-4
Exp: Using the nodetool repair command you can bring replicas in sync. There is various option Available like providing end of the token whether you want to repair the full repair or not, you want repair locally on that node, or you want to repair on the particular datacenter. Similarly, you can tell that repair should be run only on this table for primary range of the token. Primary range means the token which would be owned by that particular node.
• Remember full repair runs on all keyspace and on all the tables
• Repair runs in parallel on all nodes with the same replica data at the same time.
• You can even initiate the sequential repair.
• If you want to restrict repaired local to datacenter then use the - - dc option

Related Questions

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Question-: Once you have removed a node from the Cassandra cluster, using the “nodetool decommission� command. Which of the following is correct?
A. Node will go offline
B. JVM process would be running on this node
C. Data would not be deleted from the decommissioned node.
D. If you want to add this node back to the cluster, then you should not delete this data.


Question-: In Cassandra cluster, once of the node is trying to get the gossip info from the node, it was already doing. But somehow, it is not able to get the gossip info. Then what would happen in this case?
A. The node would not get the gossip info then it will retry after 15 mins to get the info from same node.
B. Node will become offline. As it does not have gossip info.
C. Node will try to gossip info from the next neighboring node.
D. Node will connect to the seed nodes to get the gossip info


Question-: You are running node Cassandra cluster, and you found that one of the node in the cluster is dead. You want to replace that node with the new node. Which of the following correctly applies in this situation?
A. You have to manually copy the data from the dead node to the new node. Before adding to the cluster. So that replacement is quick.
B. You must have tested this node by adding to this cluster and it may have created directories for the data, save_caches, commitlog and hints.
C. You can not replace the nodes in the single-token cluster architecture.
D. Node you are adding to the cluster must not have previous data in the data directory, saved_caches, commitlog and hints.


Question-: In your node Cassandra cluster, one of the node is down and the node is seed node. What is the next step (assuming you have nodes designated as seed node)?
A. You should quickly add replacement for this node.
B. You don’t have to worry as there two other nodes are available as seed node.
C. You should update the seed node info on each node in the Cassandra cluster.
D. Use the “nodetool removenode� command to remove that dead node, which will take care of updating seed info on each node.


Question-: You have node Cassandra cluster which is physically separated in two datacenters. nodes in each datacenter. You have found that one of the nodes is down in the Cluster (this is not a seed node). You need to replace this node from the cluster. What all are true, for replacing the node, rather than first remove and then add?
A. You don’t have to move the data two time
B. Same tokens will be used by the new replaced node.
C. Existing node will work as a backup new node.
D. Cassandra cluster would be offline for few seconds only


Question-: While replacing a dead node in the cluster you have to update the jvm.option file with the “replace_address� properties on the new node, what value it should have?
A. IP address of the seed nodes
B. IP address of the new node
C. IP address of the existing dead node
D. List of IP address for all the seed nodes