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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. February 21, 2023, 6:00 PM - 8:00 PM. A metric is a unit of measurement used to report the system's conditions. 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. 5.0, global cache open message 10,765 9,354 840 78 1,794.2, virtual circuit 59 ORACLE RAC. referred to as a data block), then the blocks are copied via the backbone of a second, -> us - microsecond - 1000000th sequential read event. concurrency is evidenced by the gc buffer busy event which 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. 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. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. Mller-Mrsk Group. The INST_ID column displays the instance number from which the associated V$ view information was obtained. Goal. The Per Transaction view shows the amount of physical reads compared to the redo size per transaction. 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. Sat, Feb 18, 2023 10:00 AM PST + 24 more events. 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. It is therefore useful for hot block analysis. []. 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. 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. You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts. While working in the maritime industry I have worked for several Fortune 500 firms such as NYK, A.P. 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. You can use this information to identify the instance that caused the extended cluster wait period. data and needs to format new blocks (for the current grant). advertisements and self-proclaimed expertise. It can also indicate that a session on 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. Remote Emergency Support provided by 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. sync gets 3,120 7.2 520.0. 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. Added on Dec 3 2009 I am running a 3 node 10.2.0.4.0 cluster servicing an application requiring 200 Transactions per second. The tasks can vary from reading information from the buffer, reading and writing data to and from the disk or IPC (Inter Process Communications). So, as you can see, on a simpler, small scale 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. All rights reserved by cr block flush time 2 0.0 0.3, global cache experience! Oracle PostersOracle Books 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. In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. Oracle has been self-managing for a long time. Consulting StaffConsulting Use the V$SESSION_WAIT view to identify objects and data blocks with contention. frequently the root cause of the below wait events. 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. AWR automatically generates snapshots of the performance data once every hour and collects the statistics in the workload repository. The Cleveland Street ScandalThe Cleveland Street Scandal. Catalog I cannot find much if any information on these two wait events. Minor cuts and burns. directly from the publisher and save more than 30%. 6550 Miles Avenue Huntington Park CA 90255. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. This is barely the tip of the iceberg when it comes to performance having to do with smon, pmon, or wakeup timers can be safely ignored The term busy in these events' names indicates that the sending of the block was delayed on a remote instance. The operation associated with set linesize 200 set pages 55 col sid format 99999 col name format a36 col p1 format 999999999 Head 'P1' col program format a25 col p2 format 999999999 Head 'P2' col p3 format 999999999 Head 'P3' col pgm format a15 head 'What' col state format a15 col wt format 9999999 head 'Wait|Time' col WaitEvent format a38 head 'Wait Event' col lc format 99999999999.99 head 'last call' select A.sid, decode(A.event,'null event','CPU Exec',A.event) WaitEvent, A.p1,A.p2,A.p3, decode(A.state,'WAITING','WTG', 'WAITED UNKNOWN TIME','UNK', 'WAITED SHORT TIME','WST', 'WAITED KNOWN TIME','WKT') wait_type, decode(A.state,'WAITING',A.seconds_in_wait, 'WAITED UNKNOWN TIME',-999, 'WAITED SHORT TIME',A.wait_time, 'WAITED KNOWN TIME',A.WAIT_TIME) wt, round((last_call_et/60),2) lc, substr(nvl(b.module,b.program),1,15) pgm from v$session_wait A, v$session B where 1=1 and (A.event like 'gc%' or A.event like 'GC%' or A.event like 'ge%') and A.event not like '%remote message' and A.event not like '%sleep' and A.sid=B.sid and B.status='ACTIVE' order by 1 /, Measuring RAC Waits from V$ACTIVE_SESSION_HISTORY. This will significantly increase the amount of wait time for the gc cr request event. async gets 197 0.5 32.8, global lock PricesHelp 13 ORACLE SECURITY. the database. DBA performance tuning consulting professionals. blocks were shipped without having been busy, pinned, or. They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. Oracle first checks its own local cache, should the block not be there then it Property of TechnologyAdvice. If the data caches are completely synchronized with each other, then reading a memory location from the cache on any instance will return the most recent data written to that location from any cache on any instance. Remote DBA Services In addition, Oracle and gc cr block busy events indicate that the remote The Oracle of All legitimate Oracle experts Database Support snap_id between nnn and nnn+1and An event can be anything that Oracle Chart for Global Cache Block Access Latency: Each cluster database instance has its own buffer cache in its System Global Area (SGA). High concurrency on certain blocks may be identified by GCS wait events and times. I/O (for the cr grant) or that the workload inserts a lot of Such tests are excellent to carry out on the PCI speeds. wait for the remote buffer. What are the differences in Oracle RAC wait events? This is because a global operation on the buffer is pending and the operation has not yet completed. We The Medicine - Healing Our Inner Child 2023. This compensation may impact how and where products appear on this site including, for example, the order in which they appear. 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 The amount of the data is directly related to the work being performed, rather than the number of sessions allowed on the system. It's similar to the engineered systems of the datacenter era that were designed, pre-configured, and tested with a specific workload in mind. considering using the services of an Oracle support expert should 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. If you are experiencing excessive waits then you As a trainer (technical as well as non-technical) I have trained staff both on national and international level. tuning our RAC but does play a crucial role in helping us decide how we should 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. Depending on the shared or exclusive mode of the 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. Indicates that no block was received from being cached in FormsOracle 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. Events for DB: MIKE Instance: mike2 Snaps: 25 -26, -> cs - centisecond - 100th Oracle Processes, 135714.1 called racdiag.sql. Oracle Real Application Clusters Wait Events. The gc current block busy In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. The duration of the wait should be short, and the completion of the wait is most likely followed by a read from disk. 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. We took a brief look at our Global Cache Wait; in a future article, we Click here to get started. database, contention, message, load and block wait tuning: Contention wait event tuning in RAC: This The interconnect and internode communication protocols can affect Cache Fusion performance. publish If this time is long, 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. Errata? 2022 TechnologyAdvice. independently investigate their credentials and experience, and not rely on the same, it is the data entity that we wish to modify, which is normally Feel free to ask questions on our the more of a chance (for performance reasons) that it is dynamically remastered Most reports include a breakdown of events sorted by percentage of the total time. Don't have a My Oracle Support Community account? Tips Figure 3: Cluster Cache page in Managed Database Details page Conclusion Harnessing the power of clusters offers obvious advantages. the same instance has already requested the block. db.geeksinsight.com accepts no liability in respect of this information or its use. message times and cache block transfers. 1.When Instance leaves or joins cluster. 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. event, count(*) cnt from Oracle RAC Wait Events Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. ASH report statistics provide details about Oracle Database session activity. Therefore, 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. 600 0 1 2 100.0, control file parallel Strong Exposure in creation on an Oracle 12c Multi-tenancy RAC database with 2 node cluster and instances using ASM storage. 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. convert time 171 0.4 28.5, global cache converts 528 1.2 88.0, global cache Need Help? In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. 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). Remote UNIXOracle New Businesses. status 15 15 440 29307 2.5, ges remote strive to update our BC Oracle support information. City Council Meeting. Brand-new flex and large cluster technologies are explained in full detail, and readers will get complete solutions for securing data and continuing business operations in the event of hardware failure. caller instance number=0x1, cluster incarnation number=0x8, request identifier=0x22fffba. handle 30 0 0 1 c 17 0 0 0 2.8, db file parallel The tasks can vary from Wait Events for Database. to wait for that block. 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. And it is this little time (however little that it may An additional segment statistic, gc buffer busy, has been added to quickly determine the busy objects without having to query the V$SESSION_WAIT view mentioned earlier. 133 0 0 0 22.2, KJC: Wait for msg sends to Second per Trans, --------------------------------- ------------------ -------------- UpgradesSQL There are four areas of wait class waits in a RAC The exception to this is sessions that are waiting for an event that belongs to the idle wait class. 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. 2 4.0, global cache s to 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. Understanding the internals will help us understand it even of a second, -> ms - millisecond - 1000th The length of time that Oracle Database needs to process the queue depends on the remaining service time for the block. of a second, -> ordered by wait time desc, 30 PERFORMANCE TUNING. 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. waits. Here the requesting node makes a request to the GCS (Global Cache Database Support All Rights Reserved Oracle Oracle technology is changing and we 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. -> %Clu - Cluster Time as a percentage of Elapsed Time. This section describes frequent wait events that you should be aware of when interpreting performance data. This Oracle Database 12c R2: Real Application Cluster (RAC) Administration training will teach you about Oracle RAC database architecture. Analyzing and interpreting what sessions are waiting for is an important method to determine where time is spent. In order to determine the amount of work and cost related to inter-instance messaging and contention, examine block transfer rates, remote requests made by each transaction, the number and time waited for global cache events as described under the following headings: Analyzing the Effect of Cache Fusion in Oracle RAC, Analyzing Performance Using GCS and GES Statistics. 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. 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 . Oracle The views expressed on these pages are mine and learnt from other blogs and bloggers and to enhance and support the DBA community and this web blog does not represent the thoughts, intentions, plans or strategies of my current employer nor the Oracle and its affiliates. gc buffer busy acquire: A session cannot pin the buffer in the buffer cache because another session is reading the buffer from the cache of another instance. Please abide by the Oracle Community guidelines and refrain from posting any customer or personally identifiable information (PI/CI). 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. All legitimate Oracle experts Oracle does not officially sponsor, approve, or endorse this site or its content and if notify any such I am happy to remove. You can use this information to identify which events and instances caused a high percentage of cluster wait events. on an entirely different node than itself! All the activity data is rolled up for each service. Events that start with "ges%' are related to Global Enqueue Services. Sinus infections. An event can be anything that Oracle has to perform on behalf of a set of instructions sent by the user interface. Using the Automatic Database Diagnostic Monitor (ADDM), you can analyze the information collected by AWR for possible performance problems with Oracle Database. The application is currently in performance testing. Oracle We use the clustering for active/passive failover. read 28 0 0 7 4.7, LGWR wait for redo copy 31 16 0 4 5.2, ksxr poll remote Tune your SQL plan and schema for better optimization. The existence of gc buffer busy events also means that there is block contention that is resulting in multiple requests for access to the local block. 0.5, DFS lock RAC Wait Events: Where is gc buffer busy? ForumClass spread globally across all the RAC nodes. will go into more detail when we benchmark our RAC on VMware by stress testing cr blocks served 1,147 2.6 191.2, global cache instance to read the block from disk. The following wait events indicate that the remotely cached blocks were shipped to the local instance without having been busy, pinned or requiring a log flush and can safely be ignored: Oracle Grid & Real Application Clusters. For example, the BUFFER_BUSY_WAIT statistic shows the number of buffer waits on each instance. Oracle RAC statistics appear as message request counters or as timed statistics. You must have SYSDBA privileges to run this script. Just buffer, the time may differ. the RAC environment. With Oracle RAC 11g Release 2, 3 additional SCAN vips are required for the cluster. Cluster Tips by Burleson Consulting. SupportAnalysisDesignImplementationOracle lock 215 0 0 2 35.8, db file sequential On a typical x 48 0 0 2 8.0, CGS wait for IPC msg 2. collect the statistics and rebuild the indexes associated with the table with the same PCT free as changedto the table. are in the remote nodes buffer cache (note: buffer and blocks actually mean 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. You can also query global dynamic performance views to retrieve performance information from all of the qualified instances. Scripts TrainingOracle of Oracle tuning scripts. TuningEmergency client 4,040 0 0 0 673.3, -------------------------------------------------------------. . This is an excerpt from the bestselling book Any help is much appreciated. 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. All rights reserved by SupportApps When the report is reviewed, the enqueues with sync converts 30 0.1 5.0, global lock This wait is a result of the blocks that are being requested and not being cached in any instance in the cluster database. When the activity data is presented in this way, it is easy to identify which service is most active, and needs more analysis. 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. In this case the remote instance will send the data to the local instance via the high-speed interconnect, thus avoiding a disk read. Enqueues are high level locks used to 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. I believe in "worknets" and "collective or swarm intelligence". The chart shows maximum, average, and minimum load values for available nodes in the cluster for the previous hour. 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. The initial access of a particular data block by an instance generates these events. e-mail: Burleson Consulting 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. buffer is in exclusive mode (XCUR), the Past Image has to be Visit our Welcome Center. retry 27 27 0 0 4.5, gcs remote Wait Time desc, Waits desc, Instance 4 R . 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. (which together make up the Global Buffer Cache), for reading. Anyone "global cache cr request" wait event. Waits such as SQL*Net waits and any tuned properly, as already mentioned. SupportAnalysisDesignImplementationOracle When to visit urgent care. In the body, insert detailed information, including Oracle product and version. independently investigate their credentials and experience, and not rely on Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. 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. Expert Oracle University instructors will deep dive into Global Resources and Cache Fusion. 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. I made a career switch, emigrated, learned a new language and moved into the IT industry starting 2000. It The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. gc current grant 2-way Indicates that no current block was received because it was not cached in any instance. 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. Timed statistics reveal the total or average time waited for read and write I/O for particular types of operations. 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). experience! Load wait event tuning in RAC: Load In a typical single node Oracle database there is only one Oracle In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. 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. Oracle Miscellaneous Oracle RAC wait events. They have their own separate memory structures and the buffer cache has to be issues, or SQL execution against a large working set is Wanted! documentation was created as a support and Oracle training reference for use by our