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Oracle 12.2 AIX 7.2 - sudden increase of cluster traffic - gc cr multi block mixed

user591200Jul 28 2020 — edited Sep 22 2020

Hi ,

I am observing cluster traffic been increased with the wait event - gc cr multi block mixed

Database								Snapshot Ids		Number of Instances		Number of Hosts		Report Total (minutes)
Id	Name	Unique Name	Role	Edition	RAC	CDB	Block Size	Begin	End	In Report	Total	In Report	Total	DB time	Elapsed time
4111447627	ABC	ABC	PRIMARY	EE	YES	YES	8192	52438	52440	3	3	3	3	576.52	30.26

Top ADDM Findings by Average Active Sessions

Finding Name	Avg active sessions of the task	Percent active sessions of finding	Task Name	Begin Snap Time	End Snap Time
Top SQL Statements	18.87	94.76	ADDM:4111447627_52439	28-Jul-20 16:00	28-Jul-20 16:15
Top SQL Statements	19.22	91.52	ADDM:4111447627_52440	28-Jul-20 16:15	28-Jul-20 16:30
Global Cache Messaging	19.22	51.05	ADDM:4111447627_52440	28-Jul-20 16:15	28-Jul-20 16:30
Global Cache Messaging	18.87	47.64	ADDM:4111447627_52439	28-Jul-20 16:00	28-Jul-20 16:15
Top Segments by "User I/O" and "Cluster"	19.22	31.99	ADDM:4111447627_52440	28-Jul-20 16:15	28-Jul-20 16:30

Top Timed Events

Instance '*' - cluster wide summary
'*' Waits, %Timeouts, Wait Time Total(s) : Cluster-wide total for the wait event
'*' 'Wait Time Avg' : Cluster-wide average computed as (Wait Time Total / Event Waits)
'*' Summary 'Avg Wait Time ' : Per-instance 'Wait Time Avg ' used to compute the following statistics
'*' [Avg/Min/Max/Std Dev] : average/minimum/maximum/standard deviation of per-instance 'Wait Time Avg'
'*' Cnt : count of instances with wait times for the event

I#	Class	Event	Waits	%Timeouts	Total(s)	Avg Wait	%DB time	Avg	Min	Max	Std Dev	Cnt
*	Cluster	gc cr multi block mixed	1,986,324	0.00	8,547.99	4.30ms	24.71	4.30ms	4.24ms	4.34ms	59.69us	3
*		DB CPU			6,315.53		18.26					3
*	User I/O	db file sequential read	4,538,481	0.00	3,946.50	869.56us	11.41	868.29us	804.89us	926.18us	60.83us	3
*	User I/O	db file parallel read	1,864,981	0.00	3,048.70	1.63ms	8.81	1.63ms	1.40ms	1.89ms	243.33us	3
*	Cluster	gc cr grant 2-way	2,686,926	0.00	2,662.63	.99ms	7.70	.99ms	.97ms	1.01ms	21.49us	3
*	Cluster	gc cr multi block grant	439,403	0.00	1,350.70	3.07ms	3.90	3.07ms	3.06ms	3.09ms	16.65us	3
*	Cluster	gc cr grant congested	286,915	0.00	1,076.50	3.75ms	3.11	3.75ms	3.63ms	3.84ms	105.31us	3
*	Cluster	gc current block 2-way	1,026,451	0.00	942.21	917.93us	2.72	918.19us	889.68us	935.78us	24.92us	3
*	Cluster	gc current block congested	176,170	0.00	766.81	4.35ms	2.22	4.35ms	4.18ms	4.48ms	155.89us	3
*	Cluster	gc current block 3-way	372,325	0.00	740.18	1.99ms	2.14	1.99ms	1.94ms	2.02ms	39.57us	3
1	Cluster	gc cr multi block mixed	676,292	0.00	2,864.57	4.24ms	24.06
1		DB CPU			2,124.48		17.85
1	User I/O	db file sequential read	1,567,041	0.00	1,451.36	926.18us	12.19
1	User I/O	db file parallel read	638,247	0.00	1,205.10	1.89ms	10.12
1	Cluster	gc cr grant 2-way	934,738	0.00	904.04	.97ms	7.59
1	Cluster	gc cr multi block grant	150,473	0.00	461.80	3.07ms	3.88
1	Cluster	gc cr grant congested	92,476	0.00	336.04	3.63ms	2.82
1	Cluster	gc current block 2-way	349,514	0.00	310.95	889.68us	2.61
1	Cluster	gc current block 3-way	127,979	0.00	248.75	1.94ms	2.09
1	Cluster	gc current block congested	54,854	0.00	229.12	4.18ms	1.92
2	Cluster	gc cr multi block mixed	663,835	0.00	2,875.72	4.33ms	24.73
2		DB CPU			2,092.05		17.99
2	User I/O	db file sequential read	1,501,318	0.00	1,311.85	873.80us	11.28
2	User I/O	db file parallel read	620,063	0.00	991.50	1.60ms	8.53
2	Cluster	gc cr grant 2-way	881,768	0.00	888.74	1.01ms	7.64
2	Cluster	gc cr multi block grant	143,855	0.00	444.89	3.09ms	3.83
2	Cluster	gc cr grant congested	94,456	0.00	356.56	3.77ms	3.07
2	Cluster	gc current block 2-way	345,140	0.00	322.98	935.78us	2.78
2	Cluster	gc current block congested	58,831	0.00	257.50	4.38ms	2.21
2	Cluster	gc current block 3-way	124,259	0.00	249.14	2.00ms	2.14
3	Cluster	gc cr multi block mixed	646,197	0.00	2,807.70	4.34ms	25.39
3		DB CPU			2,099.00		18.98
3	User I/O	db file sequential read	1,470,122	0.00	1,183.29	804.89us	10.70
3	Cluster	gc cr grant 2-way	870,420	0.00	869.85	1.00ms	7.87
3	User I/O	db file parallel read	606,671	0.00	852.10	1.40ms	7.71
3	Cluster	gc cr multi block grant	145,075	0.00	444.01	3.06ms	4.02
3	Cluster	gc cr grant congested	99,983	0.00	383.91	3.84ms	3.47
3	Cluster	gc current block 2-way	331,797	0.00	308.28	929.11us	2.79
3	Cluster	gc current block congested	62,485	0.00	280.19	4.48ms	2.53
3	Cluster	gc current block 3-way	120,087	0.00	242.29	2.02ms	2.19

Top Timed Foreground Events

Foreground Activity is captured in release 11g and above
For prior releases, Foreground Activity is computed as difference between Total Activty and Background Activity
Instance '*' - cluster wide summary
'*' Waits, %Timeouts, Wait Time Total(s) : Cluster-wide total for the wait event
'*' 'Wait Time Avg' : Cluster-wide average computed as (Wait Time Total / Event Waits)
'*' Summary 'Avg Wait Time' : Per-instance 'Wait Time Avg' used to compute the following statistics
'*' [Avg/Min/Max/Std Dev] : average/minimum/maximum/standard deviation of per-instance 'Wait Time Avg'
'*' Cnt : count of instances with wait times for the event

I#	Class	Event	Waits	%Timeouts	Total(s)	Avg Wait	%DB time	Avg	Min	Max	Std Dev	Cnt
	Wait		Event		Wait Time			Summary Avg Wait Time
*	Cluster	gc cr multi block mixed	1,985,429	0.00	8,546.11	4.30ms	24.71	4.31ms	4.24ms	4.35ms	59.91us	3
*		DB CPU			6,315.53		18.26					3
*	User I/O	db file sequential read	4,529,944	0.00	3,939.57	869.67us	11.39	868.40us	805.12us	926.36us	60.79us	3
*	User I/O	db file parallel read	1,864,966	0.00	3,048.68	1.63ms	8.81	1.63ms	1.40ms	1.89ms	243.34us	3
*	Cluster	gc cr grant 2-way	2,685,351	0.00	2,661.43	.99ms	7.69	.99ms	.97ms	1.01ms	21.43us	3
*	Cluster	gc cr multi block grant	439,077	0.00	1,349.74	3.07ms	3.90	3.07ms	3.06ms	3.09ms	16.07us	3
*	Cluster	gc cr grant congested	286,780	0.00	1,076.08	3.75ms	3.11	3.75ms	3.63ms	3.84ms	105.09us	3
*	Cluster	gc current block 2-way	1,022,458	0.00	938.85	918.22us	2.71	918.50us	889.73us	936.15us	25.13us	3
*	Cluster	gc current block congested	175,644	0.00	764.56	4.35ms	2.21	4.35ms	4.18ms	4.49ms	157.41us	3
*	Cluster	gc current block 3-way	371,477	0.00	738.56	1.99ms	2.14	1.99ms	1.94ms	2.02ms	40.67us	3
1	Cluster	gc cr multi block mixed	676,000	0.00	2,863.85	4.24ms	24.06
1		DB CPU			2,124.48		17.85
1	User I/O	db file sequential read	1,563,557	0.00	1,448.42	926.36us	12.17
1	User I/O	db file parallel read	638,240	0.00	1,205.09	1.89ms	10.12
1	Cluster	gc cr grant 2-way	933,936	0.00	903.45	.97ms	7.59
1	Cluster	gc cr multi block grant	150,391	0.00	461.55	3.07ms	3.88
1	Cluster	gc cr grant congested	92,408	0.00	335.84	3.63ms	2.82
1	Cluster	gc current block 2-way	348,379	0.00	309.96	889.73us	2.60
1	Cluster	gc current block 3-way	127,770	0.00	248.20	1.94ms	2.08
1	Cluster	gc current block congested	54,687	0.00	228.34	4.18ms	1.92
2	Cluster	gc cr multi block mixed	663,596	0.00	2,875.33	4.33ms	24.73
2		DB CPU			2,092.05		17.99
2	User I/O	db file sequential read	1,499,704	0.00	1,310.29	873.70us	11.27
2	User I/O	db file parallel read	620,060	0.00	991.50	1.60ms	8.53
2	Cluster	gc cr grant 2-way	881,436	0.00	888.48	1.01ms	Comments Post Details Added on Jul 28 2020 #connection, #performance, #performance-availability, #real-application-clusters 1 comment 1,584 views --- --- Test Email Share Subscribe Resources for Careers Developers Investors Partners Researchers Students and Educators Why Oracle Analyst Reports Best cloud-based ERP Cloud Economics Corporate Responsibility Diversity and Inclusion Security Practices Learn What is cloud computing? What is CRM? What is Docker? What is Kubernetes? What is Python? What is SaaS? Resources Try Oracle Cloud Free Training Arm for Developers Cloud Architecture Center Reference Architectures Solution Playbooks Red Bull Racing Stay Connected Developer Newsletter Events Developer Live Blog - Developer Blog - Cloud Infrastructure Oracle Developer Community Twitter - Oracle Developers © Copyright 2025 Site Map Privacy / Do Not Sell My Info Transparency Ad Choices Careers Community Integrity Policy Built with love using Oracle APEX