UpgradesSQL Thanks! Cache coherency statistics measure how well the data in caches on multiple instances is synchronized. The 'cr request retry' waits take about 0.9 seconds each. 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. The initial access of a particular data block by an instance generates these events. Does anyone know how to track down cluster wait events in an active/passive wait situation? Comparing CPU time to wait time helps to determine how much of the response time is consumed with useful work rather than waiting for resources that are potentially held by other processes. 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). The most common wait events related to this are gc cr request and gc buffer busy. New to My Oracle Support Community? See All Articles by Columnist Tarry Singh. time should be tuned first. 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. 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. Contact Geek DBA Team, via email. Tips referred to as a data block), then the blocks are copied via the backbone In the following NON-RAC environment. It is not affected by disk I/O factors other than occasional log writes. The length of time that Oracle Database needs to process the queue depends on the remaining service time for the block. Oracle 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. async converts 0 0.0 0.0, global lock events. instance received the block after a remote instance Try querying the view V$BH to The tasks can vary from The waits with the highest total 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. With Oracle RAC 10g or higher, each node requires a VIP. write 141 0 1 4 23.5, enqueue disk or IPC (Inter Process Communications). 0.5, DFS lock Burleson DBA performance tuning consulting professionals. HBA = 2-port 16Gb FC HBA Disks = 1.2 TB 10K RPM Two node RAC cluster. event_id, event order by 3; Note: gets 183 0.4 30.5, global cache wait on global cache cr request. Once your interconnect is operative, you cannot significantly influence its performance. it may be that the frequently used SQL causes a lot of disk In addition, Oracle (also called the master node). With Oracle RAC 11g Release 2, 3 additional SCAN vips are required for the cluster. The data presented is rolled up from all of the running instances. 6550 Miles Avenue Huntington Park CA 90255. This Oracle A requesting node may find the requested block resides Visit urgent care* for a wide range of concerns, including: Broken bones. 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. case the wait time, which is tracked, is charged to the resource waited upon. handling the requests is equally complicated and that makes the wait events in x 48 0 0 2 8.0, CGS wait for IPC msg It can also be its own background process as well. 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. Support. cr block send time 117 0.3 19.5, global cache This Oracle Database 12c R2: Real Application Cluster (RAC) Administration training will teach you about Oracle RAC database architecture. The chart shows maximum, average, and minimum load values for available nodes in the cluster for the previous hour. TrainingOracle SupportApps FlashGrid Cloud Cluster for Oracle RAC is an engineered cloud system. 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. In a typical RAC environment, the lock mastering To get immediate Oracle The cache fusion protocol does not require I/O to data files in order to guarantee cache coherency and Oracle RAC inherently does not cause any more I/O to disk than a nonclustered instance. 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. to that node. Anyone Depending on the shared or exclusive mode of the From any location where you can access a web browser, you can manage Oracle RAC databases, application servers, host computers, and Web applications, as well as related hardware and software. The Per Transaction view shows the amount of physical reads compared to the redo size per transaction. Click here to get started. their Oracle or have a suggestion for improving our content, we would appreciate your ApplicationsOracle This wait is a result of the blocks that are being requested and not being cached in any instance in the cluster database. Conversational, Burleson Consulting You must have SYSDBA privileges to run this script. wait events indicate a slowdown in the global caching In Oracle 9i and prior, gc cr request was known as global cache cr request. the PCI speeds. The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. 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. The most common wait events related to this are gc cr request and gc buffer busy (note that in Oracle RAC 9i and earlier these wait events were known as "global cache cr request"and "global cache buffer busy" wait events). current block pin ti 12 0.0 2.0, global cache second or less, hardly a concern when compared with the 154 second All Rights Reserved Any help is much appreciated. Observed the high cluster event events in 2 node RAC do. This Oracle 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 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. does actually, but since there is the possibility of that modification having These are again point to network tuning. Cache fusion interconnect, load issues, or SQL execution against a large working set is frequently the root cause of the below wait events. Waits are a key tuning indicator. 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 RAC Cluster Tips by Burleson Consulting: This is an . You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts. 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. the same, it is the data entity that we wish to modify, which is normally of a second, -> us - microsecond - 1000000th All rights reserved by Ion Analyzing and interpreting what causes sessions to wait is an important method to determine where time is spent. 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 advertisements and self-proclaimed expertise. The aggregates are provided on the pages where the activity data is presented including: Database Performance Page, Top Activity Page, Wait Details Page and Service Details Page. we will primarily look at the Global Cache waits. 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. ASH report statistics provide details about Oracle Database session activity. 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. Setting it to FALSE will disable it. Advertise with TechnologyAdvice on Database Journal and our other IT-focused platforms. High concurrency on certain blocks may be identified by GCS wait events and times. I have been active in several industries since 1991. 2. ForumClass Here Instead a global grant was given, enabling the requesting instance to read the block from disk or modify it. The Oracle Enterprise Manager Cluster Database Performance page provides a quick glimpse of the performance statistics for a database. Minor cuts and burns. Tuning queries to access fewer blocks will often result in less contention for the same block. ASH reports present a manageable set of data by capturing only information about active sessions. You can use the INST_ID column as a filter to retrieve V$ information from a subset of available instances. UpgradesSQL 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. 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. Sinus infections. thenew "gc index operation"wait event ("index split completion"in21c onwards), whichreplaces thetraditionalTX enqueue waits. How will I know which sessions are causing these wait events? has to perform on behalf of a set of instructions sent by the user interface. In a typical single node Oracle database there is only one DBA performance tuning consulting professionals. Remote Muscle sprains or strains. 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. considering using the services of an Oracle support expert should They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. All of this information is also available as collections that have a historic view. copies the cache to the requesting node. The second highest wait is the The GCS wait events contain the file and block number for a block request in p1 and p2, respectively. The statistics snapshots generated by AWR and Statspack can be evaluated by producing reports displaying summary data such as load and cluster profiles based on regular statistics and wait events gathered on each instance. async gets 197 0.5 32.8, global lock The Cluster Database Performance page provides a quick glimpse of the performance statistics for an Oracle RAC database. 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.