DBA_HIST_INTERCONNECT_PINGS
displays information about measured latency of interconnect messages (roundtrip) from instance to instance. In Oracle Database 11g, the PING
process assesses the latencies associated with communications for each pair of instances.
Every few seconds, the process in one instance (INSTANCE_NUMBER
value) sends two messages to each instance (TARGET_INSTANCE
value). One message has a size of 500 bytes and the other has a size of 8 KB. The message is received by the PING
process on the target instance and is immediately acknowledged. The time for the roundtrip is measured and collected.
Column  Datatype  NULL  Description 

SNAP_ID 
NUMBER 
NOT NULL 
Unique snapshot ID 
DBID 
NUMBER 
NOT NULL 
Database ID for the snapshot 
INSTANCE_NUMBER 
NUMBER 
NOT NULL 
Instance number for the snapshot 
TARGET_INSTANCE 
NUMBER 
NOT NULL 
Target instance number 
CNT_500B 
NUMBER 
Number of pings of size 500 bytes from INSTANCE_NUMBER to TARGET_INSTANCE since the startup of the source instance (INSTANCE_NUMBER ) 

WAIT_500B 
NUMBER 
Sum of roundtrip times for messages of size 500 bytes from INSTANCE_NUMBER to TARGET_INSTANCE since the startup of the source instance (INSTANCE_NUMBER ). Dividing by CNT_500B gives the average latency. 

WAITSQ_500B 
NUMBER 
Sum of squares (divided by 1000) of roundtrip times for messages of size 500 bytes from INSTANCE_NUMBER to TARGET_INSTANCE since the startup of the source instance (INSTANCE_NUMBER ). When used with CNT_500B and WAIT_500B , the standard deviation of the latency can be calculated. 

CNT_8K 
NUMBER 
Number of pings of size 8 KB from INSTANCE_NUMBER to TARGET_INSTANCE since the startup of the source instance (INSTANCE_NUMBER ) 

WAIT_8K 
NUMBER 
Sum of roundtrip times for messages of size 8 KB from INSTANCE_NUMBER to TARGET_INSTANCE since the startup of the source instance (INSTANCE_NUMBER ). Dividing by CNT_8K gives the average latency. 

WAITSQ_8K 
NUMBER 
Sum of squares (divided by 1000) of roundtrip times for messages of size 8 KB from INSTANCE_NUMBER to TARGET_INSTANCE since the startup of the source instance (INSTANCE_NUMBER ). When used with CNT_8K and WAIT_8K , the standard deviation of the latency can be calculated. 