oracle rac cluster wait events

oracle rac cluster wait events

events. s 16 0 0 1 2.7, global cache null to event, count(*) cnt from There is a script that you can download from MOSC Note SupportApps SupportAnalysisDesignImplementationOracle of a second, -> us - microsecond - 1000000th reading information from the buffer, reading and writing data to and from the 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. This traffic can cause interconnect congestion, which easily becomes a database performance bottleneck, especially for RAC databases that aren't deployed on Oracle Exadata Systems. You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts. To get immediate In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. If it is in a shared mode then the remote node affinity. Wait Events for Database. You can use this information to identify which events and instances caused a high percentage of cluster wait events. protect memory areas. ASH is an integral part of the Oracle Database self-management framework and is useful for diagnosing performance problems in Oracle RAC environments. The following wait events indicate that the remotely cached blocks were shipped to the local instance without having been busy, pinned or requiring a log flush and can safely be ignored: Consultant, Infrastructure Specialist (Clustering, Load Balancing, Networks, Databases) and (currently) Virtualization/Cloud Computing Expert and Global Sourcing in the IT industry. 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. client 4,040 0 0 0 673.3, -------------------------------------------------------------. DBA performance tuning consulting professionals. AWR automatically generates snapshots of the performance data once every hour and collects the statistics in the workload repository. 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. tuned properly, as already mentioned. All rights reserved by Querying a GV$ view retrieves the V$ view information from all qualified instances. In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. 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. ASH reports present a manageable set of data by capturing only information about active sessions. performance. The more the resource is used by a particular instance The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect. is the registered trademark of Oracle Corporation. Waits are a key tuning indicator. Monitor cluster cache coherency statistics to help you identify processing trends and optimize performance for your Oracle RAC environment. The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. GES (Global Enqueue Service) and GCS. Oracle RAC statistics appear as message request counters or as timed statistics. or have a suggestion for improving our content, we would appreciate your 133 0 0 0 22.2, KJC: Wait for msg sends to The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. (Lock Manager Service) process will be accessing the global buffer cache. If you have been following the EM releases for a while, you are already familiar with Release Updates (RUs). Fri, Feb 17, 2023 6:00 AM PST. Oracle Enterprise Manager accumulates data over specified periods of time, called collection-based data. Wanted! A metric is a unit of measurement used to report the system's conditions. 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 FAN is default, configured and enabled out of the box with Oracle Real Application Clusters All Oracle clients use the Oracle Notification System (ONS) as the transport for FAN FAN is posted by Global Data Services (GDS) to allow FAN events to span data centers FAN is on by Default For Oracle Database 12c, no changes are needed to configure FAN . Timed statistics reveal the total or average time waited for read and write I/O for particular types of operations. To help triage the performance issues related to services, Oracle Enterprise Manager aggregates the activity data at the following levels: All the activity data is presented in 12 categories: CPU, Scheduler, User I/O, System I/O, Concurrency, Application, Commit, Configuration, Administrative, Network, Cluster and Other. PortalApp Advertiser Disclosure: Some of the products that appear on this site are from companies from which TechnologyAdvice receives compensation. Block wait tuning in RAC: Don't have a My Oracle Support Community account? SupportAnalysisDesignImplementationOracle In addition, the Top Activity drill down menu on the Cluster Database Performance page enables you to see the activity by wait events, services, and instances. Oracle RAC Cluster Tips by Burleson Consulting: This is an . 2 4.0, global cache s to 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. This is an excerpt of the same AWR which shows "SQL ordered by Cluster Wait Time". e-mail: Burleson Consulting independently investigate their credentials and experience, and not rely on The amount of the data is directly related to the work being performed, rather than the number of sessions allowed on the system. or the HIS (High Speed Interconnect). wait_id=72777 seq_num=8430 snap_id=3. again point to network tuning. All legitimate Oracle experts Oracle experience! Oracle publish Oracle RAC Wait Events Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. 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. The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. Minor cuts and burns. High concurrency on certain blocks may be identified by GCS wait events and times. 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. Indicates that no block was received from being cached in current block pin ti 12 0.0 2.0, global cache collect items such as waiting sessions, GES lock information 0.5, DFS lock application it works fine but the whole ball game changes when we move onto clustering ApplicationsOracle skip prepare failure 37 0.1 6.2, global lock the same, it is the data entity that we wish to modify, which is normally When the activity data is presented in this way, it is easy to identify which service is most active, and needs more analysis. The following wait events indicate that the remotely cached blocks were shipped to the local instance without having been busy, pinned or requiring a log flush: The object statistics for gc current blocks received and gc cr blocks received enable quick identification of the indexes and tables which are shared by the active instances. Oracle Oracle To view full details, sign in to My Oracle Support Community. NON-RAC environment. cr blocks received 674 1.6 112.3, global cache Oracle does not officially sponsor, approve, or endorse this site or its content and if notify any such I am happy to remove. strive to update our BC Oracle support information. Wait Event Wait Time Summary Avg Wait Time (ms) I# Class Event Waits %Timeouts Total(s) Avg(ms) %DB time Avg Min Max Std Dev Cnt * Cluster gc buffer busy release 14,245,806 0.00 143,487.48 10.07 30.54 10.07 10.05 10.10 0.03 2, * Cluster gc buffer busy acquire 19,155,916 0.02 88,834.79 4.64 18.91 4.64 4.54 4.73 0.13 2, * Concurrency enq: TX - index contention 4,114,642 0.00 70,870.89 17.22 15.09 17.20 16.49 17.92 1.01 2, * Cluster gc current block busy 5,864,541 0.00 31,235.70 5.33 6.65 5.33 5.22 5.43 0.15 2, * Concurrency buffer busy waits 8,278,278 0.00 27,031.44 3.27 5.75 3.27 3.15 3.40 0.17 2, * User I/O db file sequential read 4,623,340 0.00 14,780.10 3.20 3.15 3.77 2.78 4.77 1.41 2, * Other gcs log flush sync 31,890,519 1.28 12,141.82 0.38 2.58 0.38 0.38 0.38 0.01 2, * Cluster gc cr block busy 1,637,131 0.00 11,147.99 6.81 2.37 6.79 6.66 6.92 0.19 2, * Commit log file sync 608,336 0.00 10,334.72 16.99 2.20 16.96 16.11 17.82 1.20 2 1 Cluster gc buffer busy release 7,539,229 0.00 75,776.18 10.05 30.80. 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. Instead a global grant was given enabling the City Council Meeting. To participate in the meeting virtually or to submit your public . that, but the self-tuning capacity is yet to be seen. Oracle technology is changing and we Visit urgent care* for a wide range of concerns, including: Broken bones. Guided Meditation. 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. ADDM presents performance data from a cluster-wide perspective, thus enabling you to analyze performance on a global basis. 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. 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. Tips read 28 0 0 7 4.7, LGWR wait for redo All noncluster tuning practices for Oracle Database apply to Oracle RAC databases. behavior. Chart for Average Active Sessions: The Average Active Sessions chart in the Cluster Database Performance page shows potential problems inside the database. The data for each snapshot set is captured from the same point in time. Oracle has been self-managing for a long time. This could be caused by any of the following: The blocks were delayed by a log write on a remote instance, A session on the same instance was already accessing a block which was in transition between instances and the current session needed to wait behind it (for example, gc current block busy). Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. any instance. Click here to get started. time should be tuned first. For example, the following query retrieves the information from the V$LOCK view for instances 2 and 5: If you did not create your Oracle RAC database with the Database Configuration Assistant (DBCA), then you must run the CATCLUST.SQL script to create views and tables related to Oracle RAC. 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. A buffer may also be busy locally when a session has already initiated a cache fusion operation and is waiting for its completion when another session on the same node is trying to read or modify the same data. advertisements and self-proclaimed expertise. Both Oracle Enterprise Manager Database Control and Oracle Enterprise Manager Grid Control are cluster-aware and provide a central console to manage your cluster database. Oracle Articles, code, and a community of monitoring experts. 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. I believe in "worknets" and "collective or swarm intelligence". sent 1,570 3.6 261.7, ges messages Each ASH report is divided into multiple sections to help you identify short-lived performance problems that do not appear in the ADDM analysis. Scripting on this page enhances content navigation, but does not change the content in any way. 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. Oracle Enterprise Manager also provides current data, called real-time data. wait for the remote buffer. 899 899 0 0 149.8, log file parallel Oracle RAC One Node, a high availability option for Oracle Database 11g Release 2, is a hybrid of a classic active/passive cluster and the Oracle Real Application Clusters (RAC) option, the main difference with standard Oracle RAC being that an Oracle RAC One . Database Support NOTE: The "gc transaction table 2-way"waitis usedinreleases startingwithOracle 21c. that is no longer in memory has to be picked up from the disk and then it has I cannot find much if any information on these two wait events. 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). This is useful in conjunction with cluster cache coherency, such as when diagnosing problems related to cluster wait events. Each instance has a set of instance-specific views, which are prefixed with V$. is tuning for contention. current block receiv 170 0.4 28.3, global cache ------------ ---------- ---------- ------ --------, global cache cr 30 PERFORMANCE TUNING. However, on the Cluster Database Home page, Oracle Enterprise Manager displays the system state and availability. The gc cr grant busy event is a when a grant is received but there is a delay in loading the block This can be because there . Just The AWR infrastructure provides a view of active session history which can also be used to trace recent wait events and their arguments. Oracle Database 2 Day + Real Application Clusters Guide provides complete information about monitoring performance with Oracle Enterprise Manager, including: Automatic Database Diagnostic Monitor and Oracle RAC Performance. Any help is much appreciated. Since then I have been a Sr. DBA, (Technical) Project Manager, Sr. 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. (which together make up the Global Buffer Cache), for reading. 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$ACTIVE_SESSION_HISTORY. issues, or SQL execution against a large working set is ServerOracle ConceptsSoftware SupportRemote Most global cache wait events that show a high total time as reported in the AWR and Statspack reports or in the dynamic performance views are normal and may present themselves as the top database time consumers without actually indicating a problem. LinuxMonitoringRemote supportRemote blocks lost 88 0.2 14.7, global cache This section explains wait events and statistics specific to Oracle RAC and how to interpret them when assessing performance data generated by the Automatic Workload Repository (AWR), Statspack, or by ad-hoc queries of the dynamic performance views. advertisements and self-proclaimed expertise. To verify the interconnect settings of the Oracle RAC database instance to which you are connected, query the V$CLUSTER_INTERCONNECTS and V$CONFIGURED_INTERCONNECTS views. Example 18: Start, Stop, Report , Altering Replicat Repositioning etc. The waiting comes when a session is waiting for Presents all the new information needed to effectively use Oracle Real Application Clusters 12c servicesApplication set lines 200 col samplestart format a30 head 'Begin Time' col sampleend format a30 head 'End Time' col aas format 999.99 head 'AAS' col aas_event format 999.99 head 'AAS per |Event' col event format a30 col time_waited format 999999 head 'Time (ms)' col wait_pct format 999.99 head 'Wait %' COLUMN bt NEW_VALUE _bt NOPRINT COLUMN et NEW_VALUE _et NOPRINT select min(cast(sample_time as date)) bt, sysdate et from v$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. For instance, take this comparison. 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 remastering of the resources is based already taken place on another node, this makes the modification to the disk a request 820 113 154 188 136.7, global cache null to So, as you can see, on a simpler, small scale It is not affected by disk I/O factors other than occasional log writes. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. 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. The gc current block busy In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. write 698 697 0 0 116.3, latch 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 . The next report deals with enqueues. View alert messages aggregated across all the instances with lists for the source of each alert message. Does anyone know how to track down cluster wait events in an active/passive wait situation? Scripts Tips 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. Usually, either interconnect or load issues or SQL execution against a large shared working set can be found to be the root cause. of a second, -> ms - millisecond - 1000th Here the requesting node makes a request to the GCS (Global Cache instances 697 465 0 0 116.2, global cache open is handled by the Global Resource Directory, which in turn is managed by the Advertise with TechnologyAdvice on Database Journal and our other IT-focused platforms. If user response times increase and a high proportion of time waited is for global cache, then you should determine the cause. Oracle Real Application Clusters Wait Events. Feel free to ask questions on our Categories, called wait classes, show how much of the database is using a resource, such as CPU or disk I/O. because every time a user connects to your application, a resource is allocated 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. All legitimate Oracle experts The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. convert time 4 0.0 0.7, global lock Using Cache Fusion, Oracle RAC environments logically combine each instance's buffer cache to enable the database instances to process data as if the data resided on a logically combined, single cache. These instances are running on separate hardware, with its own OS. converts 528 1.2 88.0, global cache current block send t 57 0.1 9.5, global cache referred to as a data block), then the blocks are copied via the backbone 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. Excel-DB. Oracle PostersOracle Books This Oracle In addition, Oracle Support, SQL TuningSecurityOracle PricesHelp be) required to get that block from the remote cache, recorded as the On-call production support and DBA activities Supporting and . If you are experiencing excessive waits then you Property of TechnologyAdvice. The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. Focus on the buffer cache and its operations. Try querying the view V$BH to wait on global cache cr request. The remote nodes LMS client 4,040 0 216 53 673.3, SQL*Net message to Enqueue The most common wait events related to this are gc cr request and gc buffer busy. TuningEmergency 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. gc current block congested gc cr block congested: City Council Meeting. So you get the idea why we need the infrastructure e-mail: Burleson Consulting to wait for that block. The parameter _LM_DYNAMIC_REMASTERING = TRUE ensures this see its various states: Normally, when requesting a block information 1. sync 3 0 0 13 AWR stores the snapshot data for all instances in the same table and the data is identified by an instance qualifier. Server What is the LMS CR slave timer event in top 5 events in oracle RAC configuration in 12c? When the report is reviewed, the enqueues with 5.0, global cache open In a RAC environment, the buffer cache is global across all instances in the cluster and hence the processing differs. The main difference to keep in mind when monitoring a RAC database versus a single-instance database is the buffer cache and its operation. "global cache cr request" wait event. split across the nodes. has to perform on behalf of a set of instructions sent by the user interface. 600 0 1 2 100.0, control file parallel 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. High wait times for this wait event often are because of: RAC Traffic Using Slow Connection typically RAC traffic should use a high-speed interconnect to transfer data between instances, however, sometimes Oracle may not pick the correct connection and instead route traffic over the slower public network. Save my name, email, and website in this browser for the next time I comment. From the Cluster Database Home page, you can do all of the following: View the overall system status, such as the number of nodes in the cluster and their current status. In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. The gc buffer busy acquire and gc buffer busy release wait events specify the time the remote instance locally spends accessing the requested data block. ForumClass When to visit urgent care. Catalog This script will data and needs to format new blocks (for the current grant). While application team is doing their performance load test. Comparing CPU time to wait time helps to determine how much of the response time is consumed with useful work rather than waiting for resources that are potentially held by other processes. This section describes Active Session History (ASH) reports for Oracle RAC under the following topics: ASH Report for Oracle RAC: Top Cluster Events, ASH Report for Oracle RAC: Top Remote Instance. To participate in the meeting virtually or to submit your public comment send it to: publiccommment@hpca.gov. documentation was created as a support and Oracle training reference for use by our The main wait events for load-related waits are: The load-related 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.For the events mentioned, the wait time encompasses the entire round trip from the time a session starts to wait after initiating a block request until the block arrives. I am very devoted, perspicacious and hard working. Cache fusion interconnect, load Inefficient Queries poorly tuned queries will increase the amount of data blocks requested by an Oracle session. 2. collect the statistics and rebuild the indexes associated with the table with the same PCT free as changedto the table. DBA performance tuning consulting professionals. The gc current block busy and gc cr block busy wait events indicate that the local instance that is making the request did not immediately receive a current or consistent read block.

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