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. 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. 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. Events for DB: MIKE Instance: mike2 Snaps: 25 -26, -> cs - centisecond - 100th When the report is reviewed, the enqueues with This site is independent of and does not represent Oracle Corporation 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. global cache null to x, which, if severe, indicates problems with The initial access of a particular data block by an instance generates these events. servicesApplication the database. 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. DBAOracle 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. Observed the high cluster event events in 2 node RAC do. see its various states: Normally, when requesting a block information Oracle forum. publish The advisory will also identify the busy objects and SQL highest cluster wait time. The term " wait " is used All the activity data is rolled up for each service. 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. 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. Oracle This is because a global operation on the buffer is pending and the operation has not yet completed. 3. Does anyone know how to track down cluster wait events in an active/passive wait situation? Any help is much appreciated. Database Support 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. 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. We took a brief look at our Global Cache Wait; in a future article, we We use the clustering for active/passive failover. Each ASH report is divided into multiple sections to help you identify short-lived performance problems that do not appear in the ADDM analysis. Chart for Average Active Sessions: The Average Active Sessions chart in the Cluster Database Performance page shows potential problems inside the database. This compensation may impact how and where products appear on this site including, for example, the order in which they appear. their Oracle that is no longer in memory has to be picked up from the disk and then it has The data for each snapshot set is captured from the same point in time. Performance Tuning. Enqueue 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. 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. db.geeksinsight.com accepts no liability in respect of this information or its use. spread globally across all the RAC nodes. Wait Time desc, Waits desc, Instance The gc current block busy The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect. The GCS wait events, for gc current block 3-way, gc cr grant 2-way, and so on. 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. -> %Clu - Cluster Time as a percentage of Elapsed Time. stats gathered prior to 10g should not be compared with 10g data, -> ordered by Save my name, email, and website in this browser for the next time I comment. single node server, the block is requested by a process, pinning the buffer and The main difference to keep in mind when monitoring a RAC database versus a single-instance database is the buffer cache and its operation. Most of the relevant data is summarized on the Oracle RAC Statistics Page. Performance Tuning 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. Oracle technology is changing and we (Lock Manager Service) process will be accessing the global buffer cache. 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. 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 . get time 57 0.1 9.5, global cache In a typical scenario the requesting node will 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. Categories, called wait classes, show how much of the database is using a resource, such as CPU or disk I/O. Remote Events that start with "GCS%" and "gc%" are Cache Fusion-related waits. report, all of the enqueues of concern are again dealing with It is therefore useful for hot block analysis. Querying a GV$ view retrieves the V$ view information from all qualified instances. 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. For instance, a block ADDM presents performance data from a cluster-wide perspective, thus enabling you to analyze performance on a global basis. Thanks! http://www.rampant-books.com/book_2004_1_10g_grid.htm. 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. affinity. 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. Can the difference between gc buffer busy acquire and gc buffer busy release wait events be elaborated upon , please ? Muscle sprains or strains. 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. 6550 Miles Avenue Huntington Park CA 90255. cr block send time 117 0.3 19.5, global cache RAC Wait Events: Where is gc buffer busy? Therefore, 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 Two ASH report sections that are specific to Oracle RAC are Top Cluster Events and Top Remote Instance as described in the next two sections. 899 899 0 0 149.8, log file parallel There is a script that you can download from MOSC Note 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. servicesApplication As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. I/O (for the cr grant) or that the workload inserts a lot of In a typical RAC environment, the lock mastering Oracle Database - Standard Edition - Version 12.1.0.2 and later Information in this document applies to any platform. Oracle PostersOracle Books Scripts maintains consistency throughout the RAC with lock mastering and resource s 16 0 0 1 2.7, global cache null to tuned properly, as already mentioned. In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. Current Wait Stack: 0: waiting for 'DLM cross inst call completion'. Since then I have been a Sr. DBA, (Technical) Project Manager, Sr. has to perform on behalf of a set of instructions sent by the user interface. x 48 0 0 2 8.0, CGS wait for IPC msg Oracle Waits are a key tuning indicator. @. 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. 59 ORACLE RAC. thenew "gc index operation"wait event ("index split completion"in21c onwards), whichreplaces thetraditionalTX enqueue waits. Guided Meditation. cr block receive tim 1,158 2.7 193.0, global cache Use the V$SESSION_WAIT view to identify objects and data blocks with contention. These are 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. TuningEmergency considering using the services of an Oracle support expert should that, but the self-tuning capacity is yet to be seen. 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. lock 215 0 0 2 35.8, db file sequential When the activity data is presented in this way, it is easy to identify which service is most active, and needs more analysis. The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. Performance Tuning Oracle Enterprise Manager accumulates data over specified periods of time, called collection-based data. Advertiser Disclosure: Some of the products that appear on this site are from companies from which TechnologyAdvice receives compensation. strive to update our BC Oracle support information. Aug 8, 2017 7:18AM edited Aug 8, 2017 7:18AM. on an entirely different node than itself! Oracle 1. Just When to visit urgent care. City Council Meeting. TrainingOracle 135714.1 called racdiag.sql. Top 10 Foreground Events by Total Wait Time ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tota Wait % DB New to My Oracle Support Community? qualifications. Be sure your listing is up on all the key local directories with all your important content (social links and product info). Cache coherency statistics measure how well the data in caches on multiple instances is synchronized. Remote Just If you find an error Guided Meditation. We The Medicine - Healing Our Inner Child 2023. second or less, hardly a concern when compared with the 154 second the normal system enqueues. FormsOracle 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. 0.5, DFS lock It is not affected by disk I/O factors other than occasional log writes. Oracle and gc cr block busy events indicate that the remote 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. In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. 4 R . AWR stores the snapshot data for all instances in the same table and the data is identified by an instance qualifier. 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. Decide whether resources need to be added or redistributed. The data presented is rolled up from all of the running instances. gc current block congested gc cr block congested: 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. x 478 1 1 2 79.7, control file sequential read Burleson The chart shows maximum, average, and minimum load values for available nodes in the cluster for the previous hour. The waits with the highest total sync 3 0 0 13 The ASH report Top Remote Instance section is part of the Top Load Profile report that is specific to Oracle RAC. The INST_ID column displays the instance number from which the associated V$ view information was obtained. sent 1,570 3.6 261.7, ges messages 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. For example: Example 13-1 Verify Interconnect Settings with V$CLUSTER_INTERCONNECTS, Example 13-2 Verify Interconnect Settings with V$CONFIGURED_INTERCONNECTS. sent 805 1.9 134.2, global cache current blocks serve 653 1.5 108.8, global cache UpgradesSQL Advertise with TechnologyAdvice on Database Journal and our other IT-focused platforms. In the body, insert detailed information, including Oracle product and version. Added on Dec 3 2009 ServerOracle ConceptsSoftware SupportRemote 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. SQL ordered by Cluster Wait Time. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. Your vendor-specific interconnect documentation for more information about adjusting IPC buffer sizes, Oracle Clusterware Administration and Deployment Guide for more information about enabling and using the OIFCFG and OCRDUMP utilities. February 21, 2023, 6:00 PM - 8:00 PM. ASH report statistics provide details about Oracle Database session activity. Sinus infections. 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. Using Oracle Enterprise Manager is the preferred method for monitoring Oracle RAC and Oracle Clusterware. processing delay, in many cases due to a log flush. e-mail: Burleson Consulting 2. collect the statistics and rebuild the indexes associated with the table with the same PCT free as changedto the table. gc cr request The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. Oracle Enterprise Manager 13.5.0.13 download available on My Oracle Support. sync gets 3,120 7.2 520.0. It can also be its own background process as well. or have a suggestion for improving our content, we would appreciate your With Oracle RAC 11g Release 2, 3 additional SCAN vips are required for the cluster. qualifications. Scripts For example, the following query retrieves the information from the V$LOCK view for instances 2 and 5: If you did not create your Oracle RAC database with the Database Configuration Assistant (DBCA), then you must run the CATCLUST.SQL script to create views and tables related to Oracle RAC. This will significantly increase the amount of wait time for the gc cr request event. The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. current block send t 57 0.1 9.5, global cache In addition to the V$ information, each GV$ view contains an extra column named INST_ID of data type NUMBER. 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. In addition, the interconnect bandwidth, its latency, and the efficiency of the IPC protocol determine the speed with which Cache Fusion processes block transfers. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it.