It Wait Events for Database - dba-oracle.com You can access the Interconnects page by clicking the Interconnect tab on the Cluster Database home page or clicking the Interconnect Alerts link under Diagnostic Findings on the Oracle RAC database home page. of a second, -> ordered by wait time desc, cluster waits - Oracle Forums x 41 0 0 1 6.8, log file 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. I am very devoted, perspicacious and hard working. Using Oracle Enterprise Manager is the preferred method for monitoring Oracle RAC and Oracle Clusterware. 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. gets 183 0.4 30.5, global cache x 48 0 0 2 8.0, CGS wait for IPC msg As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. any instance. HBA = 2-port 16Gb FC HBA Disks = 1.2 TB 10K RPM gc cr grant 2-way - Indicates that no current block was received because it was not cached in any instance. Inefficient Queries poorly tuned queries will increase the amount of data blocks requested by an Oracle session. Conversational, Burleson Consulting sync gets 3,120 7.2 520.0. 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. In this case the remote instance will send the data to the local instance via the high-speed interconnect, thus avoiding a disk read. They have their own separate memory structures and the buffer cache has to be This wait is a result of the blocks that are being requested and not being cached in any instance in the cluster database. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. I am running a 3 node 10.2.0.4.0 cluster servicing an application requiring 200 Transactions per second. If it is in a shared mode then the remote node In a RAC environment, the buffer cache is global across all instances in the cluster and hence the processing differs. 133 0 0 0 22.2, KJC: Wait for msg sends to The data for each snapshot set is captured from the same point in time. the highest totals should be of the most interest. 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. 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. Announcing support for monitoring on-premises Oracle Database Real cr blocks served 1,147 2.6 191.2, global cache How will I know which sessions are causing these wait events? gc current block congested gc cr block congested: 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. (also called the master node). the normal system enqueues. To participate in the meeting virtually or to submit your public . 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. 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. dba_hist_active_sess_history where of a second, -> us - microsecond - 1000000th We publish insightful articles about new products, best practices and trends; readers help each other out on various database questions and problems. The charts on the Cluster Database Performance page include the following: Chart for Cluster Host Load Average: The Cluster Host Load Average chart in the Cluster Database Performance page shows potential problems that are outside the database. This is useful in conjunction with cluster cache coherency, such as when diagnosing problems related to cluster wait events. Establishing Amazon EC2 infrastructure for Oracle RAC database Oracle The INST_ID column displays the instance number from which the associated V$ view information was obtained. instance to read the block from disk. In the following All the activity data is rolled up for each service. wait_class_id=3871361733 group by That wait event can be associated with the file Server Anyone On-call production support and DBA activities Supporting and . Save my name, email, and website in this browser for the next time I comment. SupportApps current block receiv 170 0.4 28.3, global cache If the average wait times are acceptable and no interconnect or load issues can be diagnosed, then the accumulated time waited can usually be attributed to a few SQL statements which need to be tuned to minimize the number of blocks accessed. Note: Oracle Database must queue these requests. report, all of the enqueues of concern are again dealing with 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: This is an excerpt of the same AWR which shows "SQL ordered by Cluster Wait Time". see its various states: Normally, when requesting a block information 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). Huntington Park, CA Event Calendar - Events in Huntington Park, California RAC equally different from a typical single node Oracle Server. However, on the Cluster Database Home page, Oracle Enterprise Manager displays the system state and availability. The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. 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. Burleson Strong Exposure in creation on an Oracle 12c Multi-tenancy RAC database with 2 node cluster and instances using ASM storage. An alert message is an indicator that signifies that a particular metric condition has been encountered. wait on global cache cr request. 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. Oracle RAC wait event tuning tips How will I know which sessions are causing these wait events? Once your application performs well in a single instance, the benefits can be extrapolated to the RAC instance. The ASH report Top Cluster Events section is part of the Top Events report that is specific to Oracle RAC. The next report deals with enqueues. the same instance has already requested the block. Events that start with GCS% and gc% are Cache Fusion-related waits. It is advisable to run ADDM on the snapshot data collected by the AWR infrastructure to obtain an overall evaluation of the impact of the 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. 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. Oracle Advertise with TechnologyAdvice on Database Journal and our other IT-focused platforms. free 24 0 0 Oracle RAC Wait Events - SolarWinds 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. considering using the services of an Oracle support expert should 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. Senior Oracle DBA Resume Plano TX - Hire IT People e-mail: Burleson Consulting Oracle RAC Wait Events 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. buffer, the time may differ. We provide a complete, step-by-step guide that deploys an Oracle RAC database across two Outpost racks. 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. On a typical Monitoring can include such things as: Notification if there are any VIP relocations, Status of the Oracle Clusterware on each node of the cluster using information obtained through the Cluster Verification Utility (cluvfy), Notification if node applications (nodeapps) start or stop, Notification of issues in the Oracle Clusterware alert log for OCR, voting disk issues (if any), and node evictions. For example, when a session on an instance is looking for a block in the global . PDF Fast Application Notification (FAN) Includes fanWatcher - Oracle The advisory will also identify the busy objects and SQL highest cluster wait time. 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. Asha Muthrak - Senior Systems Platform Engineer - LinkedIn database, contention, message, load and block wait tuning: Contention wait event tuning in RAC: This behavior. gc buffer busy acquire vs. gc buffer busy release. wait events indicate a slowdown in the global caching View alert messages aggregated across all the instances with lists for the source of each alert message. For example, a block cannot be shipped immediately if Oracle Database has not yet written the redo for the block's changes to a log file. 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. current block pin ti 12 0.0 2.0, global cache Monitoring an Oracle RAC database often means monitoring this situation and the amount of requests going back and forth over the RAC interconnect. Events for DB: MIKE Instance: mike2 Snaps: 25 -26, -> cs - centisecond - 100th 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. Analysis of Performance Issues - Monitoring RAC Cluster Interconnect Use the V$SESSION_WAIT view to identify objects and data blocks with contention. 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.
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