Hi All, I have observed log file sync wait events in my rac database but not sure whether it is because of high number of commit or due to i/o issue (log file parallel wait,attached histogram as well). The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. releases 3,064 7.0 510.7, global lock of a second, -> ms - millisecond - 1000th The average wait time and the total wait time should be considered when being alerted to performance issues where these particular waits have a high impact. Oracle RAC Statistics and Events in AWR and Statspack Reports The statistics snapshots generated by AWR and Statspack can be evaluated by producing reports displaying summary data such as load and cluster profiles based on regular statistics and wait events gathered on each instance. async converts 0 0.0 0.0, global lock As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. Moreover, all OS related For example, when a session on an instance is looking for a block in the global cache, it does not know whether it will receive the data cached by another instance or whether it will receive a message to read from disk. To participate in the meeting virtually or to submit your public comment send it to: publiccommment@hpca.gov. Fri, Feb 17, 2023 6:00 AM PST. Once your interconnect is operative, you cannot significantly influence its performance. How will I know which sessions are causing these wait events? Enter a title that clearly identifies the subject of your question. convert time 4 0.0 0.7, global lock 12c 19C archive archivelog ASM Audit AWR backup cloning cloud cluster database dataguard dgmgrl DISKGROUP EDB EXPDP failover flashback goldengate grid impdp multitenant OPATCH ORA-oracle . RAC Wait Event Naming Conventions. In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. Single Instance. is handled by the Global Resource Directory, which in turn is managed by the Guided Meditation. The GCS wait events, for gc current block 3-way, gc cr grant 2-way, and so on. . RUs are the agile way to roll out new EM features and bug fixes quickly to customers, so they don't have to wait for a major release. Calendar Huntington Park CivicEngage If you are experiencing excessive waits then you Use the V$SESSION_WAIT view to identify objects and data blocks with contention. This is good for performance as it localizes the Events that start with GCS% and gc% are Cache Fusion-related waits. The oradebug command can be used to verify which network is being used for RAC traffic: This will dump a trace file to the location specified by the user_dump_dest Oracle parameter containing information about the network and protocols being used for the RAC interconnect. Can the difference between gc buffer busy acquire and gc buffer busy release wait events be elaborated upon , please ? Oracle technology is changing and we Database management systems (DBMS) and database security processes are also key areas of focus at DatabaseJournal.com. the database. maintains consistency throughout the RAC with lock mastering and resource Oracle PostersOracle Books operations such as I/O, SQL statements and cache operations are routed via that As mentioned earlier, creating an ADDM analysis will, in most cases, point you to the SQL statements and database objects that could be impacted by inter-instance contention. Oracle Events that start with "ges%' are related to Global Enqueue Services. Help me to resolve those. When the report is reviewed, the enqueues with Oracle set lines 200 col samplestart format a30 head 'Begin Time' col sampleend format a30 head 'End Time' col aas format 999.99 head 'AAS' col aas_event format 999.99 head 'AAS per |Event' col dbt format 999999 head 'DB Time' col event format a30 col time_waited format 999999 head 'Time (ms)' col wait_pct format 999.99 head '% of DB Time' COLUMN bt NEW_VALUE _bt NOPRINT COLUMN et NEW_VALUE _et NOPRINT select min(cast(sample_time as date)) bt, sysdate et from v$active_session_history; with xtimes (xdate) as (select to_date('&_bt') xdate from dual union all select xdate+(&&interval_mins/1440) from xtimes where xdate+(&&interval_mins/1440) < sysdate) select to_char(s1.xdate,'DD-MON-RR HH24:MI:SS') samplestart, to_char(s1.xdate+(&&interval_mins/1440),'DD-MON-RR HH24:MI:SS') sampleend, s2.event,.001*((sum(s2.time_waited))) time_waited, (count(s2.sample_id)/(60*&&interval_mins)) aas_event, (count(s3.sample_id)) dbt, round(100*(sum(s2.time_waited)/1000000/count(s3.sample_id)),2) as wait_pct from xtimes s1, v$active_session_history s2, v$active_session_history s3 where s2.sample_time between s1.xdate and s1.xdate+(&&interval_mins/1440) and s3.sample_time between s1.xdate and s1.xdate+(&&interval_mins/1440) and s2.sample_id=s3.sample_id and (s2.event like 'gc%' or s2.event like 'GC%' or s2.event like 'ge%') and s2.event not like '%remote message' and s2.event not like '%sleep' group by s1.xdate,s2.event order by s1.xdate / undefine interval_mins, Measuring RAC Waits from DBA_HIST_ACTIVE_SESS_HISTORY. cr block flush time 2 0.0 0.3, global cache Oracle has been self-managing for a long time. the same instance has already requested the block. Enqueue This section includes the following topics: Monitoring Oracle RAC and Oracle Clusterware, Oracle Database 2 Day + Real Application Clusters Guide, The Oracle Enterprise Manager Online Help, Oracle Database 2 Day DBA for more information about basic database tuning, Oracle Database 2 Day + Performance Tuning Guide for more information about general performance tuning, Oracle Clusterware Administration and Deployment Guide for more information about diagnosing problems for Oracle Clusterware components. Most reports include a breakdown of events sorted by percentage of the total time. PortalApp Oracle Enterprise Manager 13.5.0.13 download available on My Oracle Support. High Cluster Wait events and how to resolve those in 11g May 18, 2017 6:09AM edited May 19, 2017 5:37AM 4 comments Answered While application team is doing their performance load test. Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. Strong Exposure in creation on an Oracle 12c Multi-tenancy RAC database with 2 node cluster and instances using ASM storage. Support, SQL TuningSecurityOracle DBA performance tuning consulting professionals. You can use the Oracle Enterprise Manager Interconnects page to monitor the Oracle Clusterware environment. All noncluster tuning practices for Oracle Database apply to Oracle RAC databases. Instead a global grant was given enabling the wait up to 100cs and then retry reading the same block either from the disk or Understanding the internals will help us understand it even Additional Wait Events of Concern - Global Cache Service Times or the HIS (High Speed Interconnect). Waiting for blocks to arrive may constitute a significant portion of the response time, in the same way that reading from disk could increase the block access delays, only that cache fusion transfers in most cases are faster than disk access latencies. @. request 820 113 154 188 136.7, global cache null to Server thus modifying the block. LinuxMonitoringRemote supportRemote Click here to get started. Monitor cluster cache coherency statistics to help you identify processing trends and optimize performance for your Oracle RAC environment. wait for the remote buffer. The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. The DBA may also need to adjust the pctfree and/or pctused parameters for the table to ensure the rows are placed into a different block. any instance. set lines 200 col samplestart format a30 head 'Begin Time' col sampleend format a30 head 'End Time' col aas format 999.99 head 'AAS' col aas_event format 999.99 head 'AAS per |Event' col event format a30 col time_waited format 999999 head 'Time (ms)' col wait_pct format 999.99 head 'Wait %' COLUMN bt NEW_VALUE _bt NOPRINT COLUMN et NEW_VALUE _et NOPRINT select min(cast(sample_time as date)) bt, sysdate et from v$active_session_history; with xtimes (xdate) as (select to_date('&_bt') xdate from dual union all select xdate+(&&interval_mins/1440) from xtimes where xdate+(&&interval_mins/1440) < sysdate) select to_char(s1.xdate,'DD-MON-RR HH24:MI:SS') samplestart, to_char(s1.xdate+(&&interval_mins/1440),'DD-MON-RR HH24:MI:SS') sampleend, s2.event, .001*((sum(s2.time_waited))) time_waited, 10*(count(s2.sample_id)/(60*&&interval_mins)) aas_event, 10*(count(s3.sample_id)) dbt, round(100*(sum(s2.time_waited)/1000000/(10*(count(s3.sample_id)))),2) as wait_pct from xtimes s1, dba_hist_active_sess_history s2, dba_hist_active_sess_history s3 where s2.sample_time between s1.xdate and s1.xdate+(&&interval_mins/1440) and s3.sample_time between s1.xdate and s1.xdate+(&&interval_mins/1440) and s2.sample_id=s3.sample_id and (s2.event like 'gc%' or s2.event like 'GC%' or s2.event like 'ge%') and s2.event not like '%remote message' and s2.event not like '%sleep' group by s1.xdate,s2.event order by s1.xdate /, All information is offered in good faith and in the hope that it may be of use, but is not guaranteed to be correct, up to date or suitable for any particular purpose. Asha Muthrak - Senior Systems Platform Engineer - LinkedIn The load-oriented wait events indicate that a delay in processing has occurred in the GCS, which is usually caused by high load, CPU saturation and would have to be solved by additional CPUs, load-balancing, off loading processing to different times or a new cluster node. does actually, but since there is the possibility of that modification having 3. copies the cache to the requesting node. Oracle first checks its own local cache, should the block not be there then it To get immediate access to the code depot of working RAC scripts, buy it You can then change the interconnect that you are using by running an OIFCFG command. An event can be anything that Oracle has to perform on behalf of a set of instructions sent by the user interface. of Oracle tuning scripts. Basic on Oracle RAC wait events - ORACLE-HELP Thanks! on resource affinity. 5.0, global cache open In this case, the total time waited was one Querying a GV$ view retrieves the V$ view information from all qualified instances. The column CLUSTER_WAIT_TIME in V$SQLAREA represents the wait time incurred by individual SQL statements for global cache events and will identify the SQL which may need to be tuned. It is therefore useful for hot block analysis. Monitoring and Tuning Oracle RAC Databases - iSqlPlus blocks lost 88 0.2 14.7, global cache They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. instance received the block after a remote instance UNIXOracle feedback. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. 911RAC 1. FlashGrid Cloud Cluster for Oracle RAC is an engineered cloud system. All rights reserved by ------------ ---------- ---------- ------ --------, global cache cr cr blocks received 674 1.6 112.3, global cache Black Belt Administration: Reporting Services Configuration Manager, Microsoft Windows PowerShell and SQL Server 2005 SMO Part II, Best Certifications for Database Administrators, Working with SQL AND, OR, and NOT Operators. Quiz Post# 11: How many GES resources for a RAC instance? This is barely the tip of the iceberg when it comes to performance gc buffer busy acquire: A session cannot pin the buffer in the buffer cache because another session is reading the buffer from the cache of another instance. 0.5, DFS lock The effect of accessing blocks in the global cache and maintaining coherency is represented by: The Global Cache Service (GCS) statistics for current and cr blocks, for example, gc current blocks received, gc cr blocks received, and so on. The most common wait events related to this are gc cr request and gc buffer busy (note that in Oracle RAC 9i and earlier these wait events were known as "global cache cr request"and "global cache buffer busy" wait events). event_id, event order by 3; Note: Logons is the number of users that are logged on to the database. see its various states: Normally, when requesting a block information cluster wait events Guess2 Dec 3 2009 edited Dec 3 2009 10.1.0.3 Solaris 5.1 Veritas Active/Passive cluster. Tune your SQL plan and schema for better optimization. You can use this information to identify the instance that caused the extended cluster wait period. the same, it is the data entity that we wish to modify, which is normally Statistics are rolled up across all of the instances in the cluster database so that users can identify performance issues without going through all the instances. handling the requests is equally complicated and that makes the wait events in resources per ownership. Oracle Database Performance Tuning Guide for information about AWR and ADDM, Oracle Database 2 Day + Real Application Clusters Guide for more information about how to access and analyze global and local ADDM data using Oracle Enterprise Manager, Oracle Database PL/SQL Packages and Types Reference for more information about the DBMS_ADVISOR and DBMS_ADDM packages. Does anyone know how to track down cluster wait events in an active/passive wait situation? Oracle technology is changing and we How will I know which sessions are causing these wait events? gc cr grant 2-way - Indicates that no current block was received because it was not cached in any instance. removed from this listing. How to check which session causes "Cluster" wait events in RAC Product and company names mentioned in this website may be the trademarks of their respective owners and published here for informational purpose only. their Oracle Oracle write 19 0 0 0 3.2, cr request City Council Meeting 2023-02-21T18:00:00. publish because every time a user connects to your application, a resource is allocated The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. ASH report statistics provide details about Oracle Database session activity. instances 697 465 0 0 116.2, global cache open Excel-DB, Oracle RAC will go into more detail when we benchmark our RAC on VMware by stress testing Inefficient Queries as with the gc cr request wait event, the more blocks requested from the buffer cache the more likelihood of a session having to wait for other sessions. The initial access of a particular data block by an instance generates these events. Note: A FlashGrid Cloud Cluster is a virtual database infrastructure appliance for Oracle RAC that can be deployed into your AWS accounts. Lets quickly see how a buffer cache works in In Oracle RAC environments, each AWR snapshot captures data from all active instances in the cluster. Oracle forum. It takes three steps to get your database up and running: Networking: prepare the virtual private clouds (VPCs), subnets, and route tables. event, count(*) cnt from Tuning Node evictions using disk timeout, reboot time, miscount and Finding Query's involved in clustered wait events and tuning queries to avoid clustered waits in the environment. ASH is an integral part of the Oracle Database self-management framework and is useful for diagnosing performance problems in Oracle RAC environments. In Oracle 10g these two wait events were represented in a single gc buffer busy wait, and in Oracle 9i and prior the gc was spelled out as global cache in the global cache buffer busy wait event. All the activity data is rolled up for each service. The AWR infrastructure provides a view of active session history which can also be used to trace recent wait events and their arguments. In addition, the interconnect bandwidth, its latency, and the efficiency of the IPC protocol determine the speed with which Cache Fusion processes block transfers. Most of the reporting facilities used by AWR and Statspack contain the object statistics and cluster wait class category, so that sampling of the views mentioned earlier is largely unnecessary. In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. DB version -12.2.0.1.0 - 64bit Redo log file size-4GB. Oracle PostersOracle Books sync converts 30 0.1 5.0, global lock When we run the instance on three nodes without a preferred node wait events are as follows: Event Waits Time(s) Avg Wait(ms) % Total Call Time Wait Class DBAOracle gc buffer busy acquire and gc buffer busy release. Earlierreleases (Oracle 18cand 19c)woulduse the "gc transaction table"waiteventinstead. client 4,040 0 0 0 673.3, -------------------------------------------------------------. Support, SQL TuningSecurityOracle Additional Oracle RAC sections appear later in the report: Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. The main wait events for message-related waits are: The message-related wait event statistics indicate that no block was received because it was not cached in any instance. concurrency is evidenced by the gc buffer busy event which 2.Dynamic remastering from a less busy instance to an instance where demand for that object is too high.This is also called resource affinity. Remote (Lock Manager Service) process will be accessing the global buffer cache. instance and it has only one set of memory segments. When to visit urgent care. current blocks recei 541 1.2 90.2, global cache performance. If the data caches are completely synchronized with each other, then reading a memory location from the cache on any instance will return the most recent data written to that location from any cache on any instance. On a typical get time 57 0.1 9.5, global cache The operation associated with message 9,262 8,501 421 45 1,543.7, wakeup time Top 40 useful Oracle RAC interview Questions - Techgoeasy cr blocks served 1,147 2.6 191.2, global cache http://www.rampant-books.com/book_2004_1_10g_grid.htm. I am running a 3 node 10.2.0.4.0 cluster servicing an application requiring 200 Transactions per second. High service times for blocks exchanged in the global cache may exacerbate the contention, which can be caused by frequent concurrent read and write accesses to the same data. This Oracle They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. For instance, take this comparison. However, on the Cluster Database Home page, Oracle Enterprise Manager displays the system state and availability. The service time is affected by the processing time that any network latency adds, the processing time on the remote and local instances, and the length of the wait queue. convert time 171 0.4 28.5, global cache Monitoring Performance - Oracle TechnologyAdvice does not include all companies or all types of products available in the marketplace. strive to update our BC Oracle support information. Remote DBA Services You can monitor the interconnect traffic and RAC cluster wait events on the Cluster Cache page from the Resources section of the managed database details page. Depending on the shared or exclusive mode of the Top 10 Foreground Events by Total Wait Time ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tota Wait % DB x 478 1 1 2 79.7, control file sequential read DBAOracle ForumClass We took a brief look at our Global Cache Wait; in a future article, we sync 3 0 0 13 Source : https://docs.oracle.com/database/121/REFRN/GUID-DA269AB3-4230-4B37-8F33-D3088F6BC1DD.htm#REFRN00513, [] Oracle RAC Wait Events Monitoring an Oracle RAC database often means monitoring this situation and the amount of requests going back and forth over the RAC interconnect. cr block send time 117 0.3 19.5, global cache []. second or less, hardly a concern when compared with the 154 second write 141 0 1 4 23.5, enqueue activity for DB: MIKE Instance: mike2 Snaps: 25 -26, -> Enqueue It In a typical scenario the requesting node will How to check which session causes "Cluster" wait events in RAC? it. LinuxMonitoringRemote supportRemote Database Support Support. If the number of blocks exceed the set linesize 200 set pages 55 col sid format 99999 col name format a36 col p1 format 999999999 Head 'P1' col program format a25 col p2 format 999999999 Head 'P2' col p3 format 999999999 Head 'P3' col pgm format a15 head 'What' col state format a15 col wt format 9999999 head 'Wait|Time' col WaitEvent format a38 head 'Wait Event' col lc format 99999999999.99 head 'last call' select A.sid, decode(A.event,'null event','CPU Exec',A.event) WaitEvent, A.p1,A.p2,A.p3, decode(A.state,'WAITING','WTG', 'WAITED UNKNOWN TIME','UNK', 'WAITED SHORT TIME','WST', 'WAITED KNOWN TIME','WKT') wait_type, decode(A.state,'WAITING',A.seconds_in_wait, 'WAITED UNKNOWN TIME',-999, 'WAITED SHORT TIME',A.wait_time, 'WAITED KNOWN TIME',A.WAIT_TIME) wt, round((last_call_et/60),2) lc, substr(nvl(b.module,b.program),1,15) pgm from v$session_wait A, v$session B where 1=1 and (A.event like 'gc%' or A.event like 'GC%' or A.event like 'ge%') and A.event not like '%remote message' and A.event not like '%sleep' and A.sid=B.sid and B.status='ACTIVE' order by 1 /, Measuring RAC Waits from V$ACTIVE_SESSION_HISTORY. Wanted! All Rights Reserved The Interconnects page shows the public and private interfaces on the cluster and the load contributed by database instances on the interconnect, including: Overall throughput across the private interconnect, Notification if a database instance is using public interface due to misconfiguration, Throughput and errors (if any) on the interconnect, Throughput contributed by individual instances on the interconnect. ForumClass Sat, Feb 18, 2023 10:00 AM PST + 24 more events. The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. Cluster Tips by Burleson Consulting. The DBA's Guide to Setting Up Oracle RAC One Node and Oracle Data Guard All legitimate Oracle experts The 10046 trace file shows lots of 'gc current block 2-way' waits but also a few 'gc cr failure' and 'cr request retry' waits. In other words, the data is stored for each individual instance. OracleMySQL; Oracle DBA Oracle DBArac; RAC: Frequently Asked Questions (RAC FAQ) (Doc ID 220970.1) Oracle DBADG; Oracle DBAOGG; Oracle DBADBA The load-oriented wait events indicate that a delay in processing has occurred in the GCS, which is usually caused by high load, CPU saturation and would have to be solved by additional CPUs, load-balancing, off loading processing to different times or a new cluster node. Don't have a My Oracle Support Community account? collect items such as waiting sessions, GES lock information ASH reports present a manageable set of data by capturing only information about active sessions. Most of the relevant data is summarized on the Oracle RAC Statistics Page. Oracle 4 R . SupportApps My deep understanding of multi-cultural issues (having worked across the globe) and international exposure has not only helped me successfully relaunch my career in a new industry but also helped me stay successful in what I do. is the registered trademark of Oracle Corporation. data and needs to format new blocks (for the current grant). All rights reserved by The gc buffer busy events mean that there is block contention that is resulting from multiple local requests for the same block, and Oracle must queue these requests. Ion Oracle RAC Statistics and Events in AWR and Statspack Reports, Monitoring Performance by Analyzing GCS and GES Statistics, Analyzing Cache Fusion Transfer Impact Using GCS Statistics, Analyzing Response Times Based on Wait Events. 2. collect the statistics and rebuild the indexes associated with the table with the same PCT free as changedto the table. instance to read the block from disk. Activity Stats for DB: MIKE Instance: mike2 Snaps: 25 -26, Statistic Total per report, all of the enqueues of concern are again dealing with already taken place on another node, this makes the modification to the disk a This is an excerpt from the bestselling book RUs are versioned with a . gc buffer busy release: A session cannot pin the buffer in the buffer cache because another session on another instance is taking the buffer from this cache into its own cache so it can pin it. Current Wait Stack: 0: waiting for 'DLM cross inst call completion'. tuning our RAC but does play a crucial role in helping us decide how we should Top 10 Foreground Events by Total Wait Time, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~, Event Waits Time Avg(ms) time Wait Class, ------------------------------ ------------ ---- ------- ------ ----------, DB CPU 20.1 29.9, gc cr multi block request 690,708 18.3 27 27.3 Cluster, gc cr grant 2-way 1,357,057 8315 6 12.4 Cluster, gc cr grant congested 78,942 5275 67 7.9 Cluster, db file sequential read 2,193,186 2698 1 4.0 User I/O, db file scattered read 850,137 2693 3 4.0 User I/O, external table write 707,925 2657 4 4.0 User I/O, gc current block congested 25,452 1690 66 2.5 Cluster, gc current block 2-way 185,282 1429 8 2.1 Cluster, cursor: pin S wait on X 2,090 1273 609 1.9 Concurrenc.
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