Activate ADDM analysis using the advisor framework through Advisor Central in Oracle Enterprise Manager, or through the DBMS_ADVISOR and DBMS_ADDM PL/SQL packages. convert time 4 0.0 0.7, global lock It is therefore useful for hot block analysis. 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. In order to determine the amount of work and cost related to inter-instance messaging and contention, examine block transfer rates, remote requests made by each transaction, the number and time waited for global cache events as described under the following headings: Analyzing the Effect of Cache Fusion in Oracle RAC, Analyzing Performance Using GCS and GES Statistics. 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. This will significantly increase the amount of wait time for the gc cr request event. current block pin ti 12 0.0 2.0, global cache In this case, the total time waited was one How will I know which sessions are causing these wait events? documentation was created as a support and Oracle training reference for use by our status 15 15 440 29307 2.5, ges remote The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. The remastering of the resources is based You can use this information to identify the instance that caused the extended cluster wait period. wait events indicate a slowdown in the global caching Fri, Feb 17, 2023 6:00 AM PST. Each instance has a set of instance-specific views, which are prefixed with V$. The load-oriented wait events indicate that a delay in processing has occurred in the GCS, which is usually caused by high load, CPU saturation and would have to be solved by additional CPUs, load-balancing, off loading processing to different times or a new cluster node. TechnologyAdvice does not include all companies or all types of products available in the marketplace. The term " wait " is used to collect additional RAC specific data: Note: 135714.1 Script to Collect RAC Diagnostic Information (racdiag.sql) The output of the script has tips for how to read the output. Oracle e-mail: Burleson Consulting It is useful to start with an ADDM report, which analyzes the routinely collected performance statistics with respect to their impact, and points to the objects and SQL contributing most to the time waited, and then moves on to the more detailed reports produced by AWR and Statspack. I am very devoted, perspicacious and hard working. ASH is an integral part of the Oracle Database self-management framework and is useful for diagnosing performance problems in Oracle RAC environments. The average wait time and the total wait time should be considered when being alerted to performance issues where these particular waits have a high impact. To perform these analyses, you can run the ADDM Advisor in ADDM for Oracle RAC mode to perform an analysis of the entire cluster; in Local ADDM mode to analyze the performance of an individual instance; or in Partial ADDM mode to analyze a subset of instances. more. set lines 200 col samplestart format a30 head 'Begin Time' col sampleend format a30 head 'End Time' col aas format 999.99 head 'AAS' col aas_event format 999.99 head 'AAS per |Event' col dbt format 999999 head 'DB Time' col event format a30 col time_waited format 999999 head 'Time (ms)' col wait_pct format 999.99 head '% of DB Time' COLUMN bt NEW_VALUE _bt NOPRINT COLUMN et NEW_VALUE _et NOPRINT select min(cast(sample_time as date)) bt, sysdate et from v$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. get time 290 0.7 48.3, global lock This section describes how to monitor GCS performance by identifying objects read and modified frequently and the service times imposed by the remote access. In other word, they have to do with waits experienced in shipping current or consistent-read versions of blocks across instances in a RAC cluster, Events that start with ges% are related to Global Enqueue Services, gc current block 2-way - Indicates that a current block was sent from either the resource master requiring 1 message and 1 transfer. However, you can influence an interconnect protocol's efficiency by adjusting the interprocess communication (IPC) buffer sizes. Muscle sprains or strains. Database Support wait for the remote buffer. 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. 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. Property of TechnologyAdvice. retry 27 27 0 0 4.5, gcs remote maintains consistency throughout the RAC with lock mastering and resource This high-level view capability means that you do not have to access each individual database instance for details if you just want to see inclusive, aggregated information. In summary, the wait events for Oracle RAC convey information valuable for performance analysis. Observed the high cluster event events in 2 node RAC do. The Cluster Database Home page is similar to a noncluster Database Home page. 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. These types of enqueues cr blocks served 1,147 2.6 191.2, global cache buffer, the time may differ. -> %CPU - CPU Time as a percentage of Elapsed Time. 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. 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 requestand global cache buffer busy wait events). Ion To participate in the meeting virtually or to submit your public . In other word, they have to do with waits experienced in shipping current or consistent-read versions of blocks across instances in a RAC cluster. Oracle Database must queue these requests. ------------, gcs messages 20 million people rely on AmericanTowns each year to find & share local information. Example 18: Start, Stop, Report , Altering Replicat Repositioning etc. 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 Database 12c R2: Real Application Cluster (RAC) Administration training will teach you about Oracle RAC database architecture. This is because a global operation on the buffer is pending and the operation has not yet completed. ASH reports present a manageable set of data by capturing only information about active sessions. is tuning for contention. Feel free to ask questions on our The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. 133 0 0 0 22.2, KJC: Wait for msg sends to data and needs to format new blocks (for the current grant). In comparison to block busy wait events, a gc buffer busy event indicates that Oracle Database cannot immediately grant access to data that is stored in the local buffer cache. The tasks can vary from 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. New to My Oracle Support Community? The non-RAC related ones have been Oracle technology is changing and we Example 20: Managing Extracts for Multiple Database Homes, Example 21: Integrated Goldengate Capture, Example 3 : Configure the Extract / Replicat for Initial Load, Example 4: Configuring Online Change Synchronization after initial load, Example 5: Configuring Secondary Extract on Source (datapump Extract), Example 6: Configuring DDL Synchronization, Example 9: Conflict Resolution & Skipping Transaction, Sql Tuning Advisory & SQL Access Advisory Steps. Contact Geek DBA Team, via email. Verify So, as you can see, on a simpler, small scale local to the machine (the remote node), need to access these buffer caches Oracle Enterprise Manager also provides current data, called real-time data. You can use this information to identify which events and instances caused a high percentage of cluster wait events. This is useful in conjunction with cluster cache coherency, such as when diagnosing problems related to cluster wait events. This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma. The aggregates are provided on the pages where the activity data is presented including: Database Performance Page, Top Activity Page, Wait Details Page and Service Details Page. Chart for Average Active Sessions: The Average Active Sessions chart in the Cluster Database Performance page shows potential problems inside the database. Database Support blocks were shipped without having been busy, pinned, or. -> %Clu - Cluster Time as a percentage of Elapsed Time. Lets quickly see how a buffer cache works in Remote DBA Services The gc current block busy wait event indicates that the access to cached data blocks was delayed because they were busy either in the remote or the local cache. Excel-DB, Oracle RAC Oracle does not officially sponsor, approve, or endorse this site or its content and if notify any such I am happy to remove. again point to network tuning. If the data is not in the local buffer cache the global buffer cache will be reviewed to see if another instance already has it in their buffer cache. or the HIS (High Speed Interconnect). 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. SupportApps They have their own separate memory structures and the buffer cache has to be In this case the remote instance will send the data to the local instance via the high-speed interconnect, thus avoiding a disk read. publish Increase the PCT free for the table. 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. Oracle RAC Wait Events Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. The 'cr request retry' waits take about 0.9 seconds each. advertisements and self-proclaimed expertise. that is no longer in memory has to be picked up from the disk and then it has any instance. the more of a chance (for performance reasons) that it is dynamically remastered feedback. it may be that the frequently used SQL causes a lot of disk and gc cr block busy events indicate that the remote to perform tasks on its behalf. Oracle strive to update our BC Oracle support information. Server Oracle 2 4.0, global cache s to 4 R . 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 . Support. The exception to this is sessions that are waiting for an event that belongs to the idle wait class. select event_id, Oracle Global dynamic performance view names are prefixed with GV$. Performance Tuning. Select a discussion category from the picklist. If you have been following the EM releases for a while, you are already familiar with Release Updates (RUs). We publish insightful articles about new products, best practices and trends; readers help each other out on various database questions and problems. Oracle Enterprise Manager 13.5.0.13 download available on My Oracle Support. Although you rarely need to set the CLUSTER_INTERCONNECTS parameter, you can use it to assign a private network IP address or NIC as in the following example: If you are using an operating system-specific vendor IPC protocol, then the trace information may not reveal the IP address. Understanding the internals will help us understand it even global cache null to x, which, if severe, indicates problems with Presents all the new information needed to effectively use Oracle Real Application Clusters 12c Events that start with "GCS%" and "gc%" are Cache Fusion-related waits. Wait events for Oracle RAC include the following categories: The main wait events for block-related waits are: The block-related wait event statistics indicate that a block was received as either the result of a 2-way or a 3-way message, that is, the block was sent from either the resource master requiring 1 message and 1 transfer, or was forwarded to a third node from which it was sent, requiring 2 messages and 1 block transfer. In Oracle 11g you will see gc buffer busy acquire wait event when the global cache open request originated from the local instance and gc buffer busy release when the open request originated from a remote instance. The existence of gc buffer busy events also means that there is block contention that is resulting in multiple requests for access to the local block. report, all of the enqueues of concern are again dealing with plansRemote 1. FlashGrid Cluster: use the FlashGrid Launcher to create an Oracle RAC cluster. 1. 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).