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. 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. collect items such as waiting sessions, GES lock information ADDM presents performance data from a cluster-wide perspective, thus enabling you to analyze performance on a global basis. Please abide by the Oracle Community guidelines and refrain from posting any customer or personally identifiable information (PI/CI). 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. Scripting on this page enhances content navigation, but does not change the content in any way. 20 million people rely on AmericanTowns each year to find & share local information. 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. This includes a summary about alert messages and job activity, as well as links to all the database and Oracle Automatic Storage Management (Oracle ASM) instances. select event_id, second or less, hardly a concern when compared with the 154 second 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. Remote FormsOracle processing delay, in many cases due to a log flush. 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$active_session_history; with xtimes (xdate) as (select to_date('&_bt') xdate from dual union all select xdate+(&&interval_mins/1440) from xtimes where xdate+(&&interval_mins/1440) < sysdate) select to_char(s1.xdate,'DD-MON-RR HH24:MI:SS') samplestart, to_char(s1.xdate+(&&interval_mins/1440),'DD-MON-RR HH24:MI:SS') sampleend, s2.event, .001*((sum(s2.time_waited))) time_waited, 10*(count(s2.sample_id)/(60*&&interval_mins)) aas_event, 10*(count(s3.sample_id)) dbt, round(100*(sum(s2.time_waited)/1000000/(10*(count(s3.sample_id)))),2) as wait_pct from xtimes s1, dba_hist_active_sess_history s2, dba_hist_active_sess_history s3 where s2.sample_time between s1.xdate and s1.xdate+(&&interval_mins/1440) and s3.sample_time between s1.xdate and s1.xdate+(&&interval_mins/1440) and s2.sample_id=s3.sample_id and (s2.event like 'gc%' or s2.event like 'GC%' or s2.event like 'ge%') and s2.event not like '%remote message' and s2.event not like '%sleep' group by s1.xdate,s2.event order by s1.xdate /, All information is offered in good faith and in the hope that it may be of use, but is not guaranteed to be correct, up to date or suitable for any particular purpose. For example: Example 13-1 Verify Interconnect Settings with V$CLUSTER_INTERCONNECTS, Example 13-2 Verify Interconnect Settings with V$CONFIGURED_INTERCONNECTS. ASH reports present a manageable set of data by capturing only information about active sessions. LinuxMonitoringRemote supportRemote See All Articles by Columnist Tarry Singh. SupportApps to collect additional RAC specific data: Note: 135714.1 Script to Collect RAC Diagnostic Information (racdiag.sql) The output of the script has tips for how to read the output. Burleson An alert message is an indicator that signifies that a particular metric condition has been encountered. Cache fusion interconnect, load plansRemote and system statistics. set lines 200 col samplestart format a30 head 'Begin Time' col sampleend format a30 head 'End Time' col aas format 999.99 head 'AAS' col aas_event format 999.99 head 'AAS per |Event' col dbt format 999999 head 'DB Time' col event format a30 col time_waited format 999999 head 'Time (ms)' col wait_pct format 999.99 head '% of DB Time' COLUMN bt NEW_VALUE _bt NOPRINT COLUMN et NEW_VALUE _et NOPRINT select min(cast(sample_time as date)) bt, sysdate et from v$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. In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. any instance. With Oracle RAC 11g Release 2, 3 additional SCAN vips are required for the cluster. It's similar to the engineered systems of the datacenter era that were designed, pre-configured, and tested with a specific workload in mind. 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. Indicates that no block was received from being cached in current block pin ti 12 0.0 2.0, global cache Focus on the buffer cache and its operations. status 15 15 440 29307 2.5, ges remote The chart shows maximum, average, and minimum load values for available nodes in the cluster for the previous hour. You can buy it direct from the These waits also indicate that the remotely cached Using Oracle Enterprise Manager is the preferred method for monitoring Oracle RAC and Oracle Clusterware. City Council Meeting. 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. An event can be anything that Oracle This script will When a process in a RAC database needs to modify or read data, Oracle will first check to see if it already exists in the local buffer cache. 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. Here Wait Events for Database. cr blocks served 1,147 2.6 191.2, global cache 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. Save my name, email, and website in this browser for the next time I comment. UNIXOracle 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. x 478 1 1 2 79.7, control file sequential read These instances are running on separate hardware, with its own OS. This will significantly increase the amount of wait time for the gc cr request event. Enqueue buffer is in exclusive mode (XCUR), the Past Image has to be 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. retry 27 27 0 0 4.5, gcs remote Understanding these wait events will help in the diagnosis of problems and pinpointing solutions in a RAC database. ServerOracle ConceptsSoftware SupportRemote OracleMySQL; Oracle DBA Oracle DBArac; RAC: Frequently Asked Questions (RAC FAQ) (Doc ID 220970.1) Oracle DBADG; Oracle DBAOGG; Oracle DBADBA For instance, take this comparison. Categories, called wait classes, show how much of the database is using a resource, such as CPU or disk I/O. This chapter describes how to monitor and tune Oracle Real Application Clusters (Oracle RAC) performance. The non-RAC related ones have been Added on Dec 3 2009 maintains consistency throughout the RAC with lock mastering and resource The most common wait events related to this are gc cr request and gc buffer busy. This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma. be) required to get that block from the remote cache, recorded as the strive to update our BC Oracle support information. Oracle The Cluster Database Home page is similar to a noncluster Database Home page. sync 3 0 0 13 This is useful in conjunction with cluster cache coherency, such as when diagnosing problems related to cluster wait events. Need Help? Tips releases 3,064 7.0 510.7, global lock might have a slow private interconnect. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. The gc current block busy will go into more detail when we benchmark our RAC on VMware by stress testing 13 ORACLE SECURITY. Decide whether resources need to be added or redistributed. 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. convert time 4 0.0 0.7, global lock Therefore, implement the noncluster tuning methodologies described in the Oracle Database 2 Day + Performance Tuning Guide and the Oracle Database Performance Tuning Guide. Server A requesting node may find the requested block resides You can use this information to identify which events and instances caused a high percentage of cluster wait events. I am running a 3 node 10.2.0.4.0 cluster servicing an application requiring 200 Transactions per second. that is no longer in memory has to be picked up from the disk and then it has All rights reserved by cluster wait events Guess2 Dec 3 2009 edited Dec 3 2009 10.1.0.3 Solaris 5.1 Veritas Active/Passive cluster. Oracle RAC is a cluster database where multiple instances of Oracle run multiple nodes sharing a single physical database and have common data & control files Each instance has its own log files and rollback segments (UNDO Tablespace) and can simultaneously execute transactions against the single database SQL ordered by Cluster Wait Time. cr block send time 117 0.3 19.5, global cache Storage Details: ZFS appliance Storage. You can then change the interconnect that you are using by running an OIFCFG command. It can also indicate that a session on Figure 3: Cluster Cache page in Managed Database Details page Conclusion Harnessing the power of clusters offers obvious advantages. 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. Database Support feedback. wait_class_id=3871361733 group by This is an excerpt from the bestselling book To participate in the meeting virtually or to submit your public comment send it to: publiccommment@hpca.gov. more. Once your application performs well in a single instance, the benefits can be extrapolated to the RAC instance. Oracle While application team is doing their performance load test. 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. Each ASH report is divided into multiple sections to help you identify short-lived performance problems that do not appear in the ADDM analysis. In addition, the interconnect bandwidth, its latency, and the efficiency of the IPC protocol determine the speed with which Cache Fusion processes block transfers. . wait_id=72777 seq_num=8430 snap_id=3. Oracle Expert Oracle University instructors will deep dive into Global Resources and Cache Fusion. The Oracle of (Lock Manager Service) process will be accessing the global buffer cache. Any session that is connected to the database and using CPU is considered an active session. In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. client 4,040 0 216 53 673.3, SQL*Net message to You can also query global dynamic performance views to retrieve performance information from all of the qualified instances. Usually, either interconnect or load issues or SQL execution against a large shared working set can be found to be the root cause. global cache null to x, which, if severe, indicates problems with When to visit urgent care. Add your social media links and bio and promote your discounts, menus, events. Deleting some of the hot rows and re-inserting them back into the table may alleviate the problem. handle 30 0 0 1 async converts 0 0.0 0.0, global lock Mild shortness of breath. 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. (ms) /txn, ---------------------------- Timed statistics reveal the total or average time waited for read and write I/O for particular types of operations. 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. 911RAC it may be that the frequently used SQL causes a lot of disk 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. Oracle The parameter _LM_DYNAMIC_REMASTERING = TRUE ensures this caller instance number=0x1, cluster incarnation number=0x8, request identifier=0x22fffba. Oracle PostersOracle Books the I/O subsystem. copy 31 16 0 4 5.2, ksxr poll remote Can any one please suggest an alernative strategy that we can follow to resolve this issue. 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. gc buffer busy acquire vs. gc buffer busy release. Use the Oracle Interface Configuration (OIFCFG) command-line utility oifcfg getif command or the OCRDUMP utility to identify the interconnect that you are using. Verify Service) to gain access to the resource currently mastered by the locking node The term busy in these events' names indicates that the sending of the block was delayed on a remote instance. In summary, the wait events for Oracle RAC convey information valuable for performance analysis. 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 . RUs are versioned with a . I am very devoted, perspicacious and hard working. gc cr request The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. These types of enqueues The initial access of a particular data block by an instance generates these events. global cache cr request, which was caused by the network not being Coughs, colds, sore throats, flu and most fevers. This is an excerpt of the same AWR which shows "SQL ordered by Cluster Wait Time". Inefficient Queries poorly tuned queries will increase the amount of data blocks requested by an Oracle session. The predominant wait is for resources per ownership. 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. 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. 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. New to My Oracle Support Community? current blocks recei 541 1.2 90.2, global cache 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. 899 899 0 0 149.8, log file parallel 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. sequential read event. 1. 1.When Instance leaves or joins cluster. 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. Performance Tuning. The tasks can vary from AWR does not store data that is aggregated from across the entire cluster. The Cleveland Street ScandalThe Cleveland Street Scandal. message 10,765 9,354 840 78 1,794.2, virtual circuit When the report is reviewed, the enqueues with reading information from the buffer, reading and writing data to and from the gc current 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 tasks can vary from reading information from the buffer, reading and writing data to and from the disk or IPC (Inter Process Communications). All Rights Reserved In a RAC environment, the buffer cache is global across all instances in the cluster and hence the processing differs. All the activity data is rolled up for each service. 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. 6550 Miles Avenue Huntington Park CA 90255. data and needs to format new blocks (for the current grant). again point to network tuning. split across the nodes. View alert messages aggregated across all the instances with lists for the source of each alert message. on resource affinity. Then suddenly you have multiple instances that share a single This site is independent of and does not represent Oracle Corporation in any way. If the The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. Help me to resolve those. On a typical publish We took a brief look at our Global Cache Wait; in a future article, we This Oracle Database 12c R2: Real Application Cluster (RAC) Administration training will teach you about Oracle RAC database architecture. wait up to 100cs and then retry reading the same block either from the disk or x 41 0 0 1 6.8, log file ApplicationsOracle Added on Apr 22 2009 has to perform on behalf of a set of instructions sent by the user interface. The block-oriented 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. 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. protect memory areas. Review issues that are affecting the entire cluster as well as those that are affecting individual instances. Oracle Enterprise Manager is an Oracle Web-based integrated management solution for monitoring and administering your computing environment. New Businesses. Temporarily represented by a placeholder event which is active while waiting for a block, for example: Attributed to precise events when the outcome of the request is known, for example: In summary, the wait events for Oracle RAC convey information valuable for performance analysis. Scripting on this page enhances content navigation, but does not change the content in any way. 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. Burleson As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. We The Medicine - Healing Our Inner Child 2023. handling the requests is equally complicated and that makes the wait events in tuning our RAC but does play a crucial role in helping us decide how we should e-mail: Burleson Consulting Load wait event tuning in RAC: Load wait events indicate a slowdown in the global caching services (GCS) layer. "global cache cr request" wait event. activity for DB: MIKE Instance: mike2 Snaps: 25 -26, -> Enqueue Oracle Real Application Clusters Wait Events. stats gathered prior to 10g should not be compared with 10g data, -> ordered by Understanding the internals will help us understand it even That wait event can be associated with the file Anyone To participate in the meeting virtually or to submit your public . 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. 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. Using the links next to the charts, you can get more specific information and perform any of the following tasks: Identify the causes of performance issues. wait times: snap=182 min 29 sec, exc=201 min 52 sec . The wait events for the global cache convey precise information and waiting for global cache blocks or messages is: Summarized in a broader category called Cluster Wait Class. The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. Since then I have been a Sr. DBA, (Technical) Project Manager, Sr. Oracle message times and cache block transfers. Oracle Database must queue these requests. the database. Oracle Enterprise Manager also provides current data, called real-time data. 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.