Examine this tnsnames entry from a RAC configuration using a SCAN listener:
HR=(DESCRIPTION=
(LOAD_BALANCE =on)
(ADDRESS=(PROTOCOL=TCP)(HOST=cluster01-scan)(FORT=1521))
(CONNECT_DATA=(SERVICE_NAME=HRSRV)))
Which two statements are true about clients using this entry to connect? (Choose two.)
A.
The host name in the tnsnames entry must be changed if nodes are added or removed from the
Cluster.
B.
Clients using EZConnect can benefit from connect time load balancing because the tnsnames entry refers to a SCAN listener.
C.
Client connection requests are automatically balanced across all IP addresses defined for the SCAN.
D.
A client connection request is received by a SCAN listener that creates the connection to the least-loaded database instance.
E.
Client connection requests are automatically failed over to another SCAN listener if the chosen SCAN listener is not available.
Not A: Because the SCAN addresses resolve to the cluster, rather than to a node address in the cluster, nodes can be added to or removed from the cluster without affecting the SCAN address configuration.
Not B: EZConnect does not use tnsnames.ora
Yes C: If SCAN is used, connections are balanced across the three IP addresses defined for SCAN,…
Yes D: The SCAN listener redirects the connection request to the local listener of the instance that is least loaded…
Not E: the SCAN addresses resolve to the cluster…
Agree
SCAN answers with the hostname of the node least loaded but NOT creates a connection with the instance. D is wrong. C,E are correct
I am not sure about this, if a scan listener is not available it will fail over to another cluster node… can you support your answer? I agree that scan listener just route the connecting…
If a node where a SCAN VIP is running fails, then the SCAN VIP and its associated listener fails over to another node in the cluster. If the number of available nodes within the cluster falls to less than three, then one server hosts two SCAN VIPs and SCAN listeners.
Source:
https://docs.oracle.com/database/122/RIWIN/about-scan-listeners.htm
Correct C,D
Source:
http://www.oracle.com/technetwork/products/clustering/overview/scan-129069.pdf Page 13
Hi Jipenlee
The page 13 states:
When a SCAN Listener receives a connection request, the SCAN Listener will ch
eck for the least
loaded instance providing the requested service. It will then re
–
direct the connection request to the
local listener on the node where the least loaded instance is running. Subsequently, the client will
be given the address of the local
listener. The local listener will finally create the connection to the
database instance.
Correct: C, E
D is not correct because local listener is the one who create the conectio, not Scan Listener.
Also we have 3 Scan Listener in order to support balance and Failover. I think C and E are correct