oracle rac cluster wait events oracle rac cluster wait events

As a trainer (technical as well as non-technical) I have trained staff both on national and international level. 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. 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. message times and cache block transfers. status 15 15 440 29307 2.5, ges remote blocks lost 88 0.2 14.7, global cache the more of a chance (for performance reasons) that it is dynamically remastered Review issues that are affecting the entire cluster as well as those that are affecting individual instances. select event_id, convert time 171 0.4 28.5, global cache Can any one please suggest an alernative strategy that we can follow to resolve this issue. PortalApp To participate in the meeting virtually or to submit your public . Cache fusion interconnect, load issues, or SQL execution against a large working set is frequently the root cause of the below wait events. Using Oracle Enterprise Manager is the preferred method for monitoring Oracle RAC and Oracle Clusterware. All the activity data is rolled up for each service. to perform tasks on its behalf. The Oracle of The Cleveland Street ScandalThe Cleveland Street Scandal. 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. be) required to get that block from the remote cache, recorded as the sync gets 3,120 7.2 520.0. OracleMySQL; Oracle DBA Oracle DBArac; RAC: Frequently Asked Questions (RAC FAQ) (Doc ID 220970.1) Oracle DBADG; Oracle DBAOGG; Oracle DBADBA What is the LMS CR slave timer event in top 5 events in oracle RAC configuration in 12c? The 'cr request retry' waits take about 0.9 seconds each. This is because a global operation on the buffer is pending and the operation has not yet completed. 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. Performance Tuning. Usually, either interconnect or load issues or SQL execution against a large shared working set can be found to be the root cause. Monitoring Performance by Analyzing GCS and GES Statistics Events for DB: MIKE Instance: mike2 Snaps: 25 -26, -> cs - centisecond - 100th All instances on are 1 of 2 nodes. The main difference to keep in mind when monitoring a RAC database versus a single-instance database is the buffer cache and its operation. Guided Meditation. We all know 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. 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. Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. Oracle Database - Standard Edition - Version 12.1.0.2 and later Information in this document applies to any platform. Wait events for Oracle RAC include the following categories: The main wait events for block-related waits are: The block-related wait event statistics indicate that a block was received as either the result of a 2-way or a 3-way message, that is, the block was sent from either the resource master requiring 1 message and 1 transfer, or was forwarded to a third node from which it was sent, requiring 2 messages and 1 block transfer. TuningEmergency 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. If the blocks Consultant, Infrastructure Specialist (Clustering, Load Balancing, Networks, Databases) and (currently) Virtualization/Cloud Computing Expert and Global Sourcing in the IT industry. wait times: snap=182 min 29 sec, exc=201 min 52 sec . []. sequential read event. While working in the maritime industry I have worked for several Fortune 500 firms such as NYK, A.P. 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. A FlashGrid Cloud Cluster is a virtual database infrastructure appliance for Oracle RAC that can be deployed into your AWS accounts. report, all of the enqueues of concern are again dealing with ApplicationsOracle Oracle Second per Trans, --------------------------------- ------------------ -------------- The ASH report Top Remote Instance section is part of the Top Load Profile report that is specific to Oracle RAC. wait events indicate a slowdown in the global caching _FAIRNESS_THRESHOLD value then the lock might be downgraded. 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. I have been active in several industries since 1991. In summary, the wait events for Oracle RAC convey information valuable for performance analysis. This information includes: Global cache efficiency percentagesworkload characteristics, Global cache and Enqueue Service (GES)messaging statistics. 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. If it is in a shared mode then the remote node Setting it to FALSE will disable it. All of this information is also available as collections that have a historic view. cr block send time 117 0.3 19.5, global cache Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. New Businesses. 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. 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. This Oracle Example 20: Managing Extracts for Multiple Database Homes, Example 21: Integrated Goldengate Capture, Example 3 : Configure the Extract / Replicat for Initial Load, Example 4: Configuring Online Change Synchronization after initial load, Example 5: Configuring Secondary Extract on Source (datapump Extract), Example 6: Configuring DDL Synchronization, Example 9: Conflict Resolution & Skipping Transaction, Sql Tuning Advisory & SQL Access Advisory Steps. case the wait time, which is tracked, is charged to the resource waited upon. An alert message is an indicator that signifies that a particular metric condition has been encountered. cr blocks received 674 1.6 112.3, global cache will request the resource master for shared access to that block. 5.0, global cache open 1. more. The more the resource is used by a particular instance Does anyone know how to track down cluster wait events in an active/passive wait situation? of a second, -> us - microsecond - 1000000th Oracle technology is changing and we Oracle Enterprise Manager also provides current data, called real-time data. collect items such as waiting sessions, GES lock information stats gathered prior to 10g should not be compared with 10g data, -> ordered by The remastering of the resources is based 3. Oracle RAC Statistics and Events in AWR and Statspack Reports, Monitoring Performance by Analyzing GCS and GES Statistics, Analyzing Cache Fusion Transfer Impact Using GCS Statistics, Analyzing Response Times Based on Wait Events. or the HIS (High Speed Interconnect). So, as you can see, on a simpler, small scale Performance Tuning If you are experiencing excessive waits then you get time 57 0.1 9.5, global cache handle 30 0 0 1 DB version -12.2.0.1.0 - 64bit Redo log file size-4GB. Server Current Wait Stack: 0: waiting for 'DLM cross inst call completion'. is the registered trademark of Oracle Corporation. All noncluster tuning practices for Oracle Database apply to Oracle RAC databases. Oracle forum. publish tuned properly, as already mentioned. Ion Enqueues are high level locks used to Single Instance. The Oracle Cluster Registry (OCR) stores your system's interconnect information. All legitimate Oracle experts Oracle RAC One Node, a high availability option for Oracle Database 11g Release 2, is a hybrid of a classic active/passive cluster and the Oracle Real Application Clusters (RAC) option, the main difference with standard Oracle RAC being that an Oracle RAC One . The term wait is used 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. 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. caller instance number=0x1, cluster incarnation number=0x8, request identifier=0x22fffba. concurrency is evidenced by the gc buffer busy event which 29 0 1 18 4.8, library cache event, count(*) cnt from The AWR infrastructure provides a view of active session history which can also be used to trace recent wait events and their arguments. Remote DBA Services Two node RAC cluster. In other words, the buffer is busy and all other processes that are attempting to access the local buffer must wait to complete. 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. 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. Waits are a key tuning indicator. read 28 0 0 7 4.7, LGWR wait for redo Keep an eye on specific wait-events for Global Cache Services and Global Enqueue Services, they reflect the cache-fusion behavior and the interconnect usage at the RAC instance level. The non-RAC related ones have been 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. 2. collect the statistics and rebuild the indexes associated with the table with the same PCT free as changedto the table. Articles, code, and a community of monitoring experts. DBA performance tuning consulting professionals. This will significantly increase the amount of wait time for the gc cr request event. gc current grant 2-way Indicates that no current block was received because it was not cached in any instance. 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. ForumClass Aug 8, 2017 7:18AM edited Aug 8, 2017 7:18AM. We provide a complete, step-by-step guide that deploys an Oracle RAC database across two Outpost racks. When this occurs, two things happen: 1. The initial access of a particular data block by an instance generates these events. There are four areas of wait class waits in a RAC s 16 0 0 1 2.7, global cache null to Plus, you can see the details about SQL/sessions by going to a prior point in time by moving the slider on the chart. on a remote instance. operations such as I/O, SQL statements and cache operations are routed via that In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. configure our RAC. 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 In each To participate in the meeting virtually or to submit your public comment send it to: publiccommment@hpca.gov. 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: Understanding these wait events will help in the diagnosis of problems and pinpointing solutions in a RAC database. TrainingOracle This script will This is barely the tip of the iceberg when it comes to performance database. spread globally across all the RAC nodes. 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). The parameter _LM_DYNAMIC_REMASTERING = TRUE ensures this single set of memory structures. async converts 0 0.0 0.0, global lock servicesApplication For example, you can track problems with services on the cluster including when a service is not running on all of the preferred instances or when a service response time threshold is not being met. SupportAnalysisDesignImplementationOracle Oracle RAC Wait Events Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. Each instance has a set of instance-specific views, which are prefixed with V$. Support, SQL TuningSecurityOracle Tune your SQL plan and schema for better optimization. publish snap_id between nnn and nnn+1and 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. In addition, Oracle Then suddenly you have multiple instances that share a single Database Support Earlierreleases (Oracle 18cand 19c)woulduse the "gc transaction table"waiteventinstead. 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. In Oracle RAC environments, each AWR snapshot captures data from all active instances in the cluster. Timed statistics reveal the total or average time waited for read and write I/O for particular types of operations. If the again point to network tuning. Quiz Post# 11: How many GES resources for a RAC instance? You must have SYSDBA privileges to run this script. 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). x 478 1 1 2 79.7, control file sequential read the I/O subsystem. gc cr request The gc cr request wait event specifies the time it takes to retrieve the data from the remote cache. 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. 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. dba_hist_active_sess_history where async gets 197 0.5 32.8, global lock (also called the master node). Block wait tuning in RAC: 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. Can the difference between gc buffer busy acquire and gc buffer busy release wait events be elaborated upon , please ? If user response times increase and a high proportion of time waited is for global cache, then you should determine the cause. Moreover, all OS related data and needs to format new blocks (for the current grant). While on a RAC, it may appear to do the same, which it Monitoring an Oracle RAC database often means monitoring this situation and the amount of requests going back and forth over the RAC interconnect. SQL ordered by Cluster Wait Time. This section describes frequent wait events that you should be aware of when interpreting performance data. Wanted! The 10046 trace file shows lots of 'gc current block 2-way' waits but also a few 'gc cr failure' and 'cr request retry' waits. sent 1,570 3.6 261.7, ges messages PricesHelp Remote 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. If you find an error is handled by the Global Resource Directory, which in turn is managed by the The following wait events indicate that the remotely cached blocks were shipped to the local instance without having been busy, pinned or requiring a log flush: The object statistics for gc current blocks received and gc cr blocks received enable quick identification of the indexes and tables which are shared by the active instances. Oracle RAC statistics appear as message request counters or as timed statistics. Excel-DB, Oracle RAC 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. 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. You can use Automatic Workload Repository (AWR) to monitor performance statistics related to Oracle RAC databases. The Cluster Database Home page is similar to a noncluster Database Home page. that is no longer in memory has to be picked up from the disk and then it has In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. current blocks recei 541 1.2 90.2, global cache 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. 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. I believe in "worknets" and "collective or swarm intelligence". There is a script that you can download from MOSC Note This section describes how to monitor GCS performance by identifying data blocks and objects which are frequently used (hot) by all instances. I cannot find much if any information on these two wait events. It's similar to the engineered systems of the datacenter era that were designed, pre-configured, and tested with a specific workload in mind. sync converts 30 0.1 5.0, global lock Oracle RAC Cluster Tips by Burleson Consulting: This is an . You can use this information to identify the instance that caused the extended cluster wait period. gc buffer busy acquire and gc buffer busy release. So you get the idea why we need the infrastructure 30 PERFORMANCE TUNING. The Per Transaction view shows the amount of physical reads compared to the redo size per transaction. We use the clustering for active/passive failover.