Which two statements are true regarding server-side connect-time load balancing for a RAC database when using SCAN listeners?

Yisus is right!

“Expert Oracle RAC 12c

Service Metrics

The MMON (Memory Monitor) database background process calculates the service-level metrics using service statistics, and these metrics are visible at v$activeservice dynamic performance view. Metrics are calculated at intervals of 5 seconds and 1 minute. In the following output, the first line shows the metrics calculated at 1-minute intervals, and the second line shows the metrics calculated at 5-second intervals.

Two sets of metrics are calculated by the MMON background process, one indicating service_time and the other indicating throughput. “”Depending on the service configuration, goodness of a service is calculated and PMON (Process Monitor) or LREG (Listener Registration – 12c) background processes communicate the service metrics to the SCAN and VIP listeners””.

…
But, in version 12c, this possibility is eliminated as the LREG parameter performs service registration and PMON is freed from listener registration.

…
In version 12c, listener registration is performed by a new mandatory background process named LREG. At database start, the LREG process polls the listeners specified in the local_listener and remote_listener parameters to identify whether the listeners are running. If the listeners are available, then the services are registered to the listeners by the LREG process. The earlier command to trace listener registration in version 11.2 is applicable to
version 12c also, but the listener registration details are written to an LREG trace file instead of a PMON trace file.
”

“With server-side load balancing, the SCAN listener directs a connection request to the best instance currently providing the service, based on the -clbgoal and –rlbgoal settings for the service.”

“server-side connect-time load balancing”

“http://docs.oracle.com/database/121/HABPT/config_cw.htm#HABPT4860

Server-side load balancing When you create an Oracle RAC database with DBCA, it automatically:

Configures and enables server-side load balancing

Sets the remote listener parameter to the SCAN listener (Note: If you do not use DBCA, you should set the REMOTE_LISTENER database parameter to scan_name:scan_port.)

Creates a sample client-side load balancing connection definition in the tnsnames.ora file on the server.

To further enhance connection load balancing, use the Load Balancing Advisory and define the connection load balancing for each service. Load Balancing Advisory provides information to applications about the current service levels that the database and its instances are providing. The load balancing advisory makes recommendations to applications about where to direct application requests to obtain the best service based on the policy that you have defined for that service. Load balancing advisory events are published through ONS. There are two types of service-level goals for run-time connection load balancing:

SERVICE_TIME: Attempts to direct work requests to instances according to response time. Load balancing advisory data is based on elapsed time for work done in the service plus available bandwidth to the service. An example for the use of SERVICE_TIME is for workloads such as internet shopping where the rate of demand changes. The following example shows how to set the goal to SERVICE_TIME for connections using the online service:

srvctl modify service -d db_unique_name -s online -B SERVICE_TIME -j SHORT
THROUGHPUT: Attempts to direct work requests according to throughput. The load balancing advisory is based on the rate that work is completed in the service plus available bandwidth to the service. An example for the use of THROUGHPUT is for workloads such as batch processes, where the next job starts when the last job completes. The following example shows how to set the goal to THROUGHPUT for connections using the sjob service:

srvctl modify service -d db_unique_name -s sjob -B THROUGHPUT -j LONG

So, “C” is wrong, is not to enable, but, to use!