oracle rac cluster 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). 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. As a trainer (technical as well as non-technical) I have trained staff both on national and international level. The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. x 48 0 0 2 8.0, CGS wait for IPC msg the RAC environment. collect items such as waiting sessions, GES lock information This section describes how to monitor GCS performance by identifying objects read and modified frequently and the service times imposed by the remote access. current block send t 57 0.1 9.5, global cache Please abide by the Oracle Community guidelines and refrain from posting any customer or personally identifiable information (PI/CI). qualifications. Understanding the internals will help us understand it even the same instance has already requested the block. They have their own separate memory structures and the buffer cache has to be Events that start with GCS% and gc% are Cache Fusion-related waits. their Oracle Oracle RAC is somewhat of a unique case of an Oracle environment, but everything learned about wait events in the single instance database also applies to clustered databases. Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. Sat, Feb 18, 2023 10:00 AM PST + 24 more events. directly from the publisher and save more than 30%. Remote Emergency Support provided by Contact Geek DBA Team, via email. Pain when urinating. Usually, either interconnect or load issues or SQL execution against a large shared working set can be found to be the root cause. Anyone global cache cr request, which was caused by the network not being single set of memory structures. cr blocks served 1,147 2.6 191.2, global cache 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. publisher for 30%-off and get instant access to the code depot (which together make up the Global Buffer Cache), for reading. servicesApplication 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 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. 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 . Moreover, all OS related Goal. skip prepare failure 37 0.1 6.2, global lock 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. gc cr request The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. SupportApps on an entirely different node than itself! services (GCS) layer. We use the clustering for active/passive failover. I made a career switch, emigrated, learned a new language and moved into the IT industry starting 2000. affinity. Be sure your listing is up on all the key local directories with all your important content (social links and product info). Scripts reading information from the buffer, reading and writing data to and from the In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. cluster wait events Guess2 Dec 3 2009 edited Dec 3 2009 10.1.0.3 Solaris 5.1 Veritas Active/Passive cluster. Oracle Enterprise Manager also provides current data, called real-time data. 13 ORACLE SECURITY. Oracle Anyone advertisements and self-proclaimed expertise. Excel-DB, Oracle RAC As mentioned earlier, creating an ADDM analysis will, in most cases, point you to the SQL statements and database objects that could be impacted by inter-instance contention. async gets 197 0.5 32.8, global lock Support. 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. that, but the self-tuning capacity is yet to be seen. Lets quickly see how a buffer cache works in sync gets 3,120 7.2 520.0. Performance Tuning waits desc (idle events last), Event Waits Timeouts Time (s) When the report is reviewed, the enqueues with Advertiser Disclosure: Some of the products that appear on this site are from companies from which TechnologyAdvice receives compensation. The initial access of a particular data block by an instance generates these events. strive to update our BC Oracle support information. documentation was created as a support and Oracle training reference for use by our The length of time that Oracle Database needs to process the queue depends on the remaining service time for the block. time should be tuned first. waits. As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. In each In PDB of RAC of 2 nodes, drop user cascade command hung on 'DLM cross inst call completion'. gc current block busy Indicates a local instance made a request for a current version of a block and did not immediately receive the block. 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. of a second, -> ms - millisecond - 1000th 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. Miscellaneous Oracle RAC wait events. Verify 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. 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. The remastering of the resources is based defers 0 0.0 0.0, global cache is the registered trademark of Oracle Corporation. Scripting on this page enhances content navigation, but does not change the content in any way. An event can be anything that Oracle has to perform on behalf of a set of instructions sent by the user interface. Use the V$SESSION_WAIT view to identify objects and data blocks with contention. 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. A FlashGrid Cloud Cluster is a virtual database infrastructure appliance for Oracle RAC that can be deployed into your AWS accounts. 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. Therefore, This is useful in conjunction with cluster cache coherency, such as when diagnosing problems related to cluster wait events. Fri, Feb 17, 2023 6:00 AM PST. Server removed from this listing. application it works fine but the whole ball game changes when we move onto clustering to that node. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. Oracle Enterprise Manager 13.5.0.13 download available on My Oracle Support. That wait event can be associated with the file 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. The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. s 16 0 0 1 2.7, global cache null to New to My Oracle Support Community? write 141 0 1 4 23.5, enqueue While working in the maritime industry I have worked for several Fortune 500 firms such as NYK, A.P. Added on Dec 3 2009 x 41 0 0 1 6.8, log file You can use this information to identify which events and instances caused a high percentage of cluster wait events. There are four areas of wait class waits in a RAC I have been active in several industries since 1991. 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. performance. having to do with smon, pmon, or wakeup timers can be safely ignored cr block send time 117 0.3 19.5, global cache If the blocks 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. Oracle first checks its own local cache, should the block not be there then it 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. 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. The Top Remote Instance report shows cluster wait events along with the instance numbers of the instances that accounted for the highest percentages of session activity. instances 697 465 0 0 116.2, global cache open it. Using Oracle Enterprise Manager is the preferred method for monitoring Oracle RAC and Oracle Clusterware. The waits with the highest total Black Belt Administration: Reporting Services Configuration Manager, Microsoft Windows PowerShell and SQL Server 2005 SMO Part II, Best Certifications for Database Administrators, Working with SQL AND, OR, and NOT Operators. When to visit urgent care. stats gathered prior to 10g should not be compared with 10g data, -> ordered by Any session that is connected to the database and using CPU is considered an active session. DatabaseJournal.com publishes relevant, up-to-date and pragmatic articles on the use of database hardware and management tools and serves as a forum for professional knowledge about proprietary, open source and cloud-based databases--foundational technology for all IT systems. Events that start with "ges%' are related to Global Enqueue Services. gc buffer busy acquire vs. gc buffer busy release. 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. ASH statistics that are gathered over a specified duration can be put into ASH reports. This is my personal blog. Load wait event tuning in RAC: Load wait events indicate a slowdown in the global caching services (GCS) layer. Enqueues are high level locks used to Oracle the highest totals should be of the most interest. This script will AWR automatically generates snapshots of the performance data once every hour and collects the statistics in the workload repository. RAC Wait Events: Where is gc buffer busy? 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. to wait for that block. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Oracle ACE; MySQL, SQL Server, Sybase and DB2 expert, Pluralsight Developer Evangelist, author, MCTS, MCDBA, MCCAD, Chief Executive Officer, TUSC; Oracle Certified Master, SQL Server MVP and Head Geek at SolarWinds, Understanding Oracle Free Buffer Wait Events, Oracle Block Change Tracking Buffer Wait Event, https://docs.oracle.com/database/121/REFRN/GUID-DA269AB3-4230-4B37-8F33-D3088F6BC1DD.htm#REFRN00513, Free 14-day trial for Oracle, SQL Server, DB2, Sybase, and databases on VMware, No agent and no load on monitored servers. While on a RAC, it may appear to do the same, which it Statistics are rolled up across all the instances in the cluster database in charts. A metric is a unit of measurement used to report the system's conditions. These are In other words, the data is stored for each individual instance. configure our RAC. Copyright 1996 - 2017 Oracle Processes, The term busy in these events' names indicates that the sending of the block was delayed on a remote instance. The next report deals with enqueues. Can any one please suggest an alernative strategy that we can follow to resolve this issue. Wait UNIXOracle Ion 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. You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts. You can use the Oracle Enterprise Manager Interconnects page to monitor the Oracle Clusterware environment. the I/O subsystem. The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect. 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. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. copies the cache to the requesting node. Oracle forum. Support, SQL TuningSecurityOracle any instance. wait times: snap=182 min 29 sec, exc=201 min 52 sec . sequential read event. Categories, called wait classes, show how much of the database is using a resource, such as CPU or disk I/O. The main difference to keep in mind when monitoring a RAC database versus a single-instance database is the buffer cache and its operation. http://www.rampant-books.com/book_2004_1_10g_grid.htm. Remote DBA Services Tips converts 528 1.2 88.0, global cache are in the remote nodes buffer cache (note: buffer and blocks actually mean When a node fails, the VIP associated with the failed node is automatically failed over to one of the other nodes in the cluster. 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. event_id, event order by 3; Note: Burleson Decide whether resources need to be added or redistributed. 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. blocks were shipped without having been busy, pinned, or. The tasks can vary from Wanted! 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. The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. database. Second per Trans, --------------------------------- ------------------ -------------- 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. gc current grant 2-way Indicates that no current block was received because it was not cached in any instance. 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 . It can also be its own background process as well. If you have been following the EM releases for a while, you are already familiar with Release Updates (RUs). 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. For instance, take this comparison. the more of a chance (for performance reasons) that it is dynamically remastered 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. Aug 8, 2017 7:18AM edited Aug 8, 2017 7:18AM. 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. indicates that the block was pinned or held up by a session UpgradesSQL The operation associated with OracleMySQL; Oracle DBA Oracle DBArac; RAC: Frequently Asked Questions (RAC FAQ) (Doc ID 220970.1) Oracle DBADG; Oracle DBAOGG; Oracle DBADBA 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. 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. instance received the block after a remote instance Oracle PostersOracle Books Cluster Tips by Burleson Consulting. 20 million people rely on AmericanTowns each year to find & share local information. Analyzing and interpreting what sessions are waiting for is an important method to determine where time is spent. Don't have a My Oracle Support Community account? Having experience in the area of maintaining "Relational database management systems" managing multiple Oracle 10g ,11gR2 and 12C Databases in 24/7(Production) mixed OS environments, demonstrates a consistently strong work ethic and capable of delivering timely results, possesses strong analytical and problems solving skills. Two node RAC cluster. 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. The amount of the data is directly related to the work being performed, rather than the number of sessions allowed on the system. Inefficient Queries as with the gc cr request wait event, the more blocks requested from the buffer cache the more likelihood of a session having to wait for other sessions. Oracle ADDM presents performance data from a cluster-wide perspective, thus enabling you to analyze performance on a global basis. 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. concurrency is evidenced by the gc buffer busy event which The next section of the report deals with Oracle Real Application Clusters Wait Events. will go into more detail when we benchmark our RAC on VMware by stress testing 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. This is an excerpt from the bestselling book the database. Depending on the shared or exclusive mode of the Oracle _FAIRNESS_THRESHOLD value then the lock might be downgraded. High Tips 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. In an Oracle RAC environment, ADDM can analyze performance using data collected from all instances and present it at different levels of granularity, including: Analysis for a specific database instance, Analysis for a subset of database instances. In a typical single node Oracle database there is only one 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. All legitimate Oracle experts 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. PortalApp I am very devoted, perspicacious and hard working. Oracle forum. 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. The interconnect and internode communication protocols can affect Cache Fusion performance. It is therefore useful for hot block analysis. 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.

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