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those metrics shows the effect of accessing blocks in the global cache and maintaining cache coherency.
basically, the response time for Cache Fusion transfers is determined by the messaging time and
processing time imposed by the physical interconnect components, the IPC protocol, and the
therefore, Inter-Instance performance issues can be caused by:
1) Under configured network settings at the OS
2) dropped packets,retransmits, or cyclic redundancy check errors (CRC)
3) large number of processes in the run queue waiting for CPU
4) high value for the DB_FILE_MULTIBLOCK_READ_COUNT
Note also that poor SQL or bad optimization paths can cause additional block gets via the interconnect, just as not using ASSM for Locally Managed Tablespaces, or not using CACHE NOORDER for sequence, ...
This message is reporting metrics on the average amount of time it takes an instance to obtain a current copy of a data block via the cluster interconnect from another instance in the cluster. By default, Any block transfers across the interconnect would ideally be performed in less than 10ms(i.e 1 centi seconds).
METRIC_NAME is "GC_AVG_CR_GET_TIME" Refer the below URL for the same:
If the frequency of these alerts are very minimal and no Performance issue reported, we can ignore this. Any performance issue is reported along with these Grid/OEM alerts, please consider investigating the issue at Network/Interconnect level.
Edited by: 977730 on Dec 19, 2012 1:09 AM