Observed the high cluster event events in 2 node RAC do. Once your interconnect is operative, you cannot significantly influence its performance. Your vendor-specific interconnect documentation for more information about adjusting IPC buffer sizes, Oracle Clusterware Administration and Deployment Guide for more information about enabling and using the OIFCFG and OCRDUMP utilities. 135714.1 called racdiag.sql. admin@sh008.global.temp.domains, All about Database Administration, Tips & Tricks, Time Series Analysis Predict Alerts & Events, OML4PY Embedded Python Libraries in Oracle Database, Database Service Availability Summary Grafana Dashboard, Oracle 19c & 20c : Machine Learning Additions into Database, Oracle 19c: Automatic flashback in standby following primary database flashback, Oracle 19c: Max_Idle_Blocker_Time Parameter, Example 1: GoldenGate Setup & Configuration, Example 10: Reporting Commands in Goldengate, Example 14: Auto Starting Extract & Replicat, More Manager Parameters, Example 16: Different Versions of Goldengate Replication, Example 17: Start, Stop, Report, Altering Extract Regenerating, Rolling Over etc. event, count(*) cnt from Waits such as SQL*Net waits and any to that node. This section describes how to monitor GCS performance by identifying data blocks and objects which are frequently used (hot) by all instances. For instance, take this comparison. When you log in to Oracle Enterprise Manager using a client browser, the Cluster Database Home page appears where you can monitor the status of both Oracle Clusterware and the Oracle RAC environments. Oracle Grid & Real Application Clusters. frequently the root cause of the below wait events. The waits with the highest total 911RAC This information includes: Global cache efficiency percentagesworkload characteristics, Global cache and Enqueue Service (GES)messaging statistics. Ion There are four areas of wait class waits in a RAC 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. Oracle 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. feedback. Enqueues are high level locks used to We use the clustering for active/passive failover. an action, sometimes from a user and at other times from the database. It can also be its own background process as well. Performance Tuning. FormsOracle These are Top 5 Timed Events Avg %Total ~~~~~ wait Call Event Waits Time (s) (ms) Time The ASH report Top Cluster Events section is part of the Top Events report that is specific to Oracle RAC. Tune your SQL plan and schema for better optimization. Any increases in the average wait times for the events mentioned in the preceding list could be caused by the following occurrences: High load: CPU shortages, long run queues, scheduling delays, Misconfiguration: using public instead of private interconnect for message and block traffic. Monitoring Performance by Analyzing GCS and GES Statistics If you find an error more. The Top Cluster Events report lists events that account for the highest percentage of session activity in the cluster wait class event along with the instance number of the affected instances. This section describes how to monitor GCS performance by identifying objects read and modified frequently and the service times imposed by the remote access. Oracle gc cr block 2-way - Indicates that a cr block was sent from either the resource master requiring 1 message and 1 transfer, gc cr block 3-way -Indicates that a current block was forwarded to a 3rd node from which it was sent, requiring 2 messages and one block transfer. The exception to this is sessions that are waiting for an event that belongs to the idle wait class. In an Oracle RAC environment, ADDM can analyze performance using data collected from all instances and present it at different levels of granularity, including: Analysis for a specific database instance, Analysis for a subset of database instances. Burleson Consulting TrainingOracle Oracle write 19 0 0 0 3.2, cr request sequential read event. The response time for cache fusion transfers is determined by the messaging and processing times imposed by the physical interconnect components, the IPC protocol and the GCS protocol. The Oracle of is tuning for contention. 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. If this time is long, Expert Oracle University instructors will deep dive into Global Resources and Cache Fusion. 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. Focus on the buffer cache and its operations. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. message 9,262 8,501 421 45 1,543.7, wakeup time As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. Message wait tuning in RAC: This Analyzing and interpreting what sessions are waiting for is an important method to determine where time is spent. Remote The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. UNIXOracle In the body, insert detailed information, including Oracle product and version. The predominant wait is for considering using the services of an Oracle support expert should 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. single node server, the block is requested by a process, pinning the buffer and 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). Here Quiz Post# 11: How many GES resources for a RAC instance? The second highest wait is the -> %Total - Cluster Time as a percentage of Total Cluster Wait Time. ForumClass Coughs, colds, sore throats, flu and most fevers. If you have been following the EM releases for a while, you are already familiar with Release Updates (RUs). In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. 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. Plus, you can see the details about SQL/sessions by going to a prior point in time by moving the slider on the chart. Brand-new flex and large cluster technologies are explained in full detail, and readers will get complete solutions for securing data and continuing business operations in the event of hardware failure. In an excerpt of the AWR report below, I'm seeing several wait events with "Cluster" as the wait class in a RAC environment with 5 nodes and whose version is 11gR2. Instead a global grant was given enabling the it may be that the frequently used SQL causes a lot of disk has to perform on behalf of a set of instructions sent by the user interface. Remote Emergency Support provided by current blocks serve 653 1.5 108.8, global cache Database Support Added on Apr 22 2009 of a second, -> ms - millisecond - 1000th 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. The main wait events for contention-related waits are: The contention-related wait event statistics indicate that a block was received which was pinned by a session on another node, was deferred because a change had not yet been flushed to disk or because of high concurrency, and therefore could not be shipped immediately. 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. you see that the local buffer cache operations are not really local and are report, all of the enqueues of concern are again dealing with 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. Events for DB: MIKE Instance: mike2 Snaps: 25 -26, -> cs - centisecond - 100th You can buy it direct from the Activity Stats for DB: MIKE Instance: mike2 Snaps: 25 -26, Statistic Total per Contact Geek DBA Team, via email. 29 POSTGRES. That wait event can be associated with the file For example, when a session on an instance is looking for a block in the global . Categories, called wait classes, show how much of the database is using a resource, such as CPU or disk I/O. Wanted! Just the PCI speeds. An event can be anything that Oracle Use the Oracle Interface Configuration (OIFCFG) command-line utility oifcfg getif command or the OCRDUMP utility to identify the interconnect that you are using. This wait is a result of the blocks that are being requested and not being cached in any instance in the cluster database. get time 290 0.7 48.3, global lock The gc current block busy is the registered trademark of Oracle Corporation. dba_hist_active_sess_history where The non-RAC related ones have been Oracle has been self-managing for a long time. because every time a user connects to your application, a resource is allocated The most common wait events related to this are gc cr request and gc buffer busy. The initial access of a particular data block by an instance generates these events. cr blocks served 1,147 2.6 191.2, global cache SupportApps However, on the Cluster Database Home page, Oracle Enterprise Manager displays the system state and availability. Keep an eye on specific wait-events for Global Cache Services and Global Enqueue Services, they reflect the cache-fusion behavior and the interconnect usage at the RAC instance level. A metric is a unit of measurement used to report the system's conditions. disk or IPC (Inter Process Communications). 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. independently investigate their credentials and experience, and not rely on Events that start with "ges%' are related to Global Enqueue Services. We publish insightful articles about new products, best practices and trends; readers help each other out on various database questions and problems. We all know This is good for performance as it localizes the UpgradesSQL directly from the publisher and save more than 30%. Any session that is connected to the database and using CPU is considered an active session. All legitimate Oracle experts in most situations. defers 0 0.0 0.0, global cache tuning our RAC but does play a crucial role in helping us decide how we should 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. Enqueue gc current grant 2-way Indicates that no current block was received because it was not cached in any instance. buffer, the time may differ. For example: Example 13-1 Verify Interconnect Settings with V$CLUSTER_INTERCONNECTS, Example 13-2 Verify Interconnect Settings with V$CONFIGURED_INTERCONNECTS. Wanted! The tasks can vary from DBA performance tuning consulting professionals. Most Oracle DBAs go for wait_class_id=3871361733 group by Copyright 1996 - 2020 Monitor cluster cache coherency statistics to help you identify processing trends and optimize performance for your Oracle RAC environment. DatabaseJournal.com publishes relevant, up-to-date and pragmatic articles on the use of database hardware and management tools and serves as a forum for professional knowledge about proprietary, open source and cloud-based databases--foundational technology for all IT systems. (Lock Manager Service) process will be accessing the global buffer cache. snap_id between nnn and nnn+1and About Oracle RAC Global Cache CR Request Wait Event By Richard Niemiec on April 7, 2013 When a process requires one or more blocks, Oracle first checks whether it has those (blocks) in its local cache.
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