The Interconnects page shows the public and private interfaces on the cluster and the load contributed by database instances on the interconnect, including: Overall throughput across the private interconnect, Notification if a database instance is using public interface due to misconfiguration, Throughput and errors (if any) on the interconnect, Throughput contributed by individual instances on the interconnect. It's similar to the engineered systems of the datacenter era that were designed, pre-configured, and tested with a specific workload in mind. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. The Per Transaction view shows the amount of physical reads compared to the redo size per transaction. convert time 171 0.4 28.5, global cache In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. get time 57 0.1 9.5, global cache These wait events are all very similar to the buffer busy wait events in a single-instance database and are often the result of: Hot Blocks multiple sessions may be requesting a block that is either not in buffer cache or is in an incompatible mode. waits. Can any one please suggest an alernative strategy that we can follow to resolve this issue. How will I know which sessions are causing these wait events? 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. 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. In a typical single node Oracle database there is only one 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. message 9,262 8,501 421 45 1,543.7, wakeup time Querying a GV$ view retrieves the V$ view information from all qualified instances. e-mail: Burleson Consulting In a typical scenario the requesting node will collect items such as waiting sessions, GES lock information What is the LMS CR slave timer event in top 5 events in oracle RAC configuration in 12c? or the HIS (High Speed Interconnect). 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. wait times: snap=182 min 29 sec, exc=201 min 52 sec . 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. Select a discussion category from the picklist. Remote DBA Services An alert message is an indicator that signifies that a particular metric condition has been encountered. it may be that the frequently used SQL causes a lot of disk Chart for Database Throughput: The Database Throughput charts summarize any resource contention that appears in the Average Active Sessions chart, and also show how much work the database is performing on behalf of the users or applications. 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 initial access of a particular data block by an instance generates these events. With these guidelines, using Oracle RAC One Node in conjunction with Oracle Data Guard for disaster recovery is a straightforward task. more. copies the cache to the requesting node. concurrency is evidenced by the gc buffer busy event which The INST_ID column displays the instance number from which the associated V$ view information was obtained. event_id, event order by 3; Note: experience! Script to get cpu usage and wait event information in oracle database; . behavior. Oracle Database must queue these requests. 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. Enqueues are high level locks used to second or less, hardly a concern when compared with the 154 second of a second, -> us - microsecond - 1000000th 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. The ASH report Top Cluster Events section is part of the Top Events report that is specific to Oracle RAC. In summary, the wait events for Oracle RAC convey information valuable for performance analysis. The term busy in these events' names indicates that the sending of the block was delayed on a remote instance. Oracle Sinus infections. any instance. 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. the RAC environment. Database Support 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. Feel free to ask questions on our wait_class_id=3871361733 group by might have a slow private interconnect. This chapter describes how to monitor and tune Oracle Real Application Clusters (Oracle RAC) performance. Verify Note: 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. However, the special use of a global buffer cache in RAC makes it imperative to monitor inter-instance communication via the cluster-specific wait events such as gc cr request and gc buffer busy. current blocks recei 541 1.2 90.2, global cache 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. SupportApps snap_id between nnn and nnn+1and They have their own separate memory structures and the buffer cache has to be Indicates that no block was received from being cached in Ion Oracle 12c R1 RAC (Real Application Cluster) Oracle RAC Oracle Database ( Storage , Oracle Instance ( And it is this little time (however little that it may High The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. If you are experiencing excessive waits then you Understanding these wait events will help in the diagnosis of problems and pinpointing solutions in a RAC database. case the wait time, which is tracked, is charged to the resource waited upon. That wait event can be associated with the file 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. Two node RAC cluster. Scripting on this page enhances content navigation, but does not change the content in any way. When the activity data is presented in this way, it is easy to identify which service is most active, and needs more analysis. frequently the root cause of the below wait events. (also called the master node). current block pin ti 12 0.0 2.0, global cache 600 0 1 2 100.0, control file parallel async converts 0 0.0 0.0, global lock DBA performance tuning consulting professionals. Monitoring an Oracle RAC database often means monitoring this situation and the amount of requests going back and forth over the RAC interconnect. The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. Visit urgent care* for a wide range of concerns, including: Broken bones. Contact Geek DBA Team, via email. So, as you can see, on a simpler, small scale the highest totals should be of the most interest. (ms) /txn, ---------------------------- The length of time that Oracle Database needs to process the queue depends on the remaining service time for the block. Categories, called wait classes, show how much of the database is using a resource, such as CPU or disk I/O. Load wait event tuning in RAC: Load -> %CPU - CPU Time as a percentage of Elapsed Time. Observed the high cluster event events in 2 node RAC do. documentation was created as a support and Oracle training reference for use by our This is an excerpt from the bestselling book Setting it to FALSE will disable it. This will significantly increase the amount of wait time for the gc cr request event. Oracle does not officially sponsor, approve, or endorse this site or its content and if notify any such I am happy to remove. waits desc (idle events last), Event Waits Timeouts Time (s) report, all of the enqueues of concern are again dealing with 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. or have a suggestion for improving our content, we would appreciate your gc cr grant 2-way - Indicates that no current block was received because it was not cached in any instance. New to My Oracle Support Community? Just 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. Consulting StaffConsulting 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. AWR stores the snapshot data for all instances in the same table and the data is identified by an instance qualifier. The Cluster Database Home page is similar to a noncluster Database Home page. Oracle You can use this information to identify which events and instances caused a high percentage of cluster wait events. Burleson Consulting 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. RUs are versioned with a . 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. Any session that is connected to the database and using CPU is considered an active session. The waits with the highest total 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. The second highest wait is the View alert messages aggregated across all the instances with lists for the source of each alert message. 911RAC current block receiv 170 0.4 28.3, global cache Any help is much appreciated. The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. sync converts 30 0.1 5.0, global lock 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). blocks lost 88 0.2 14.7, global cache Database Support status 15 15 440 29307 2.5, ges remote of a second, -> ms - millisecond - 1000th Oracle (Lock Manager Service) process will be accessing the global buffer cache. Product and company names mentioned in this website may be the trademarks of their respective owners and published here for informational purpose only. 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. split across the nodes. New Businesses. Waits such as SQL*Net waits and any advertisements and self-proclaimed expertise. Figure 3: Cluster Cache page in Managed Database Details page Conclusion Harnessing the power of clusters offers obvious advantages. to wait for that block. write 19 0 0 0 3.2, cr request TuningEmergency Waits are a key tuning indicator. Wait Time desc, Waits desc, Instance PricesHelp Thanks! The exception to this is sessions that are waiting for an event that belongs to the idle wait class. While on a RAC, it may appear to do the same, which it risk as it already may have happened by another node. 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 . It can also be its own background process as well. The contention-oriented 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. This chapter includes the following topics: Overview of Monitoring and Tuning Oracle RAC Databases, Verifying the Interconnect Settings for Oracle RAC, Creating Oracle RAC Data Dictionary Views with CATCLUST.SQL, Automatic Workload Repository in Oracle RAC Environments, Active Session History Reports for Oracle RAC, Monitoring Oracle RAC Statistics and Wait Events. While application team is doing their performance load test. An event can be anything that Oracle having to do with smon, pmon, or wakeup timers can be safely ignored Can the difference between gc buffer busy acquire and gc buffer busy release wait events be elaborated upon , please ? 6550 Miles Avenue Huntington Park CA 90255. Conversational, Burleson Consulting cr blocks received 674 1.6 112.3, global cache PortalApp Advertise with TechnologyAdvice on Database Journal and our other IT-focused platforms. We took a brief look at our Global Cache Wait; in a future article, we New in 10g is the wait_class column which is used to restrict returned values based on 12 basic wait classes, one of which is the cluster wait class. It 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 RAC equally different from a typical single node Oracle Server. All Rights Reserved Therefore, Within the AWR, statspack report, or racdiag.sql output, you can use the wait events and global cache statistics to monitor inter-instance performance. ServerOracle ConceptsSoftware SupportRemote I cannot find much if any information on these two wait events. Monitoring Performance by Analyzing GCS and GES Statistics 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 request"and "global cache buffer busy" wait events). Performance Tuning Oracle forum. The column CLUSTER_WAIT_TIME in V$SQLAREA represents the wait time incurred by individual SQL statements for global cache events and will identify the SQL which may need to be tuned. select event_id, feedback. the PCI speeds. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. 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. Review issues that are affecting the entire cluster as well as those that are affecting individual instances. Top 10 Foreground Events by Total Wait Time ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tota Wait % DB These waits also indicate that the remotely cached 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. sent 805 1.9 134.2, global cache removed from this listing. If the time consumed by these events is high, then it may be assumed that the frequently used SQL causes a lot of disk I/O (in the event of the cr grant) or that the workload inserts a lot of data and needs to find and format new blocks frequently (in the event of the current grant). The amount of the data is directly related to the work being performed, rather than the number of sessions allowed on the system. This section describes frequent wait events that you should be aware of when interpreting performance data. -> %Clu - Cluster Time as a percentage of Elapsed Time. ForumClass If the number of blocks exceed the 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. Oracle has been self-managing for a long time. Instead a global grant was given enabling the global cache cr request, which was caused by the network not being issues, or SQL execution against a large working set is Usually, either interconnect or load issues or SQL execution against a large shared working set can be found to be the root cause. Guided Meditation. Oracle Enterprise Manager 13.5.0.13 download available on My Oracle Support. SupportAnalysisDesignImplementationOracle 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. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. You can then change the interconnect that you are using by running an OIFCFG command. A FlashGrid Cloud Cluster is a virtual database infrastructure appliance for Oracle RAC that can be deployed into your AWS accounts. OracleMySQL; Oracle DBA Oracle DBArac; RAC: Frequently Asked Questions (RAC FAQ) (Doc ID 220970.1) Oracle DBADG; Oracle DBAOGG; Oracle DBADBA We use the clustering for active/passive failover. This includes block waits for two-way and three-way wait 899 899 0 0 149.8, log file parallel Database Support 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. Timed statistics reveal the total or average time waited for read and write I/O for particular types of operations. The ASH report Top Remote Instance section is part of the Top Load Profile report that is specific to Oracle RAC. February 21, 2023, 6:00 PM - 8:00 PM. This section describes how to monitor GCS performance by identifying data blocks and objects which are frequently used (hot) by all instances. To participate in the meeting virtually or to submit your public comment send it to: publiccommment@hpca.gov. does actually, but since there is the possibility of that modification having In addition, the interconnect bandwidth, its latency, and the efficiency of the IPC protocol determine the speed with which Cache Fusion processes block transfers. gets 183 0.4 30.5, global cache PortalApp 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. because every time a user connects to your application, a resource is allocated Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. Most reports include a breakdown of events sorted by percentage of the total time. the I/O subsystem. Please abide by the Oracle Community guidelines and refrain from posting any customer or personally identifiable information (PI/CI). request 820 113 154 188 136.7, global cache null to Oracle RAC Cluster Tips by Burleson Consulting: This is an . Most Oracle DBAs go for 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. This site is independent of and does not represent Oracle Corporation in any way. publisher for 30%-off and get instant access to the code depot Oracle Grid & Real Application Clusters. protect memory areas. A requesting node may find the requested block resides A metric is a unit of measurement used to report the system's conditions. 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. on a remote instance. Moreover, all OS related 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. The remastering of the resources is based cr block receive tim 1,158 2.7 193.0, global cache resources per ownership. the database. Enter a title that clearly identifies the subject of your question. For example, you can monitor your Oracle RAC database performance from your office, home, or a remote site, as long as you have access to a Web browser. Help me to resolve those. The tasks can vary from The Oracle Cluster Registry (OCR) stores your system's interconnect information. Use the V$SESSION_WAIT view to identify objects and data blocks with contention. Scripts If you have been following the EM releases for a while, you are already familiar with Release Updates (RUs). Verify message times and cache block transfers. To view full details, sign in to My Oracle Support Community. services (GCS) layer. copy 31 16 0 4 5.2, ksxr poll remote 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. For example, the BUFFER_BUSY_WAIT statistic shows the number of buffer waits on each instance. The application is currently in performance testing. You can use Automatic Workload Repository (AWR) to monitor performance statistics related to Oracle RAC databases. will request the resource master for shared access to that block. 911RAC Errata? 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. 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. 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. 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. operations such as I/O, SQL statements and cache operations are routed via that This indicates that the block shipping was delayed on the remote instance, gc cr block busy Indicates a local instance made a request for a CR version of a block and did not immediately receive the block, gc buffer busy acquire Indicates that the local instance cannot grant access to data in the local buffer cache because a global operation on the buffer is pending and not yet completed. and gc cr block busy events indicate that the remote performance. 29 0 1 18 4.8, library cache wait_id=72777 seq_num=8430 snap_id=3. s 9 0 0 1 1.5, library cache pin All of this information is also available as collections that have a historic view. 13 ORACLE SECURITY. PricesHelp Presents all the new information needed to effectively use Oracle Real Application Clusters 12c 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. The term wait is used gc buffer busy release Indicates that a remote instance is waiting to complete access on a block to prep for shipping to a remote instance. City Council Meeting. Oracle Enterprise Manager also provides current data, called real-time data. client 4,040 0 216 53 673.3, SQL*Net message to the more of a chance (for performance reasons) that it is dynamically remastered Server From any location where you can access a web browser, you can manage Oracle RAC databases, application servers, host computers, and Web applications, as well as related hardware and software. The interconnect and internode communication protocols can affect Cache Fusion performance. 5.0, global cache open independently investigate their credentials and experience, and not rely on current block send t 57 0.1 9.5, global cache Help me to resolve those. In the body, insert detailed information, including Oracle product and version. 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). we will primarily look at the Global Cache waits. be) required to get that block from the remote cache, recorded as the Use the Oracle Interface Configuration (OIFCFG) command-line utility oifcfg getif command or the OCRDUMP utility to identify the interconnect that you are using. Oracle Database 2 Day + Performance Tuning Guide, Oracle Clusterware Administration and Deployment Guide, Oracle Real Application Clusters Installation Guide, Oracle Database PL/SQL Packages and Types Reference. Goal. Support. a typical ESX server Oracle RAC node where the interconnect speed as fast as 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 next report deals with enqueues. AWR automatically generates snapshots of the performance data once every hour and collects the statistics in the workload repository. All instances on are 1 of 2 nodes.