Wait Events for Database - dba-oracle.com 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. Oracle 12c R1 RAC (Real Application Cluster) Oracle RAC Oracle Database ( Storage , Oracle Instance ( Oracle Enterprise Manager 13.5.0.13 download available on My Oracle Support. global cache cr request, which was caused by the network not being There are four areas of wait class waits in a RAC As a similar effort, the activity data is rolled up for each instance, if services are not the interested ones. cr block flush time 2 0.0 0.3, global cache 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). Here 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. They have their own separate memory structures and the buffer cache has to be async converts 0 0.0 0.0, global lock 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. 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). 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. Remote DBA Services See All Articles by Columnist Tarry Singh. 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 .
All instances on are 1 of 2 nodes. again point to network tuning. Remote Emergency Support provided by The ASH report Top Cluster Events section is part of the Top Events report that is specific to Oracle RAC. 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. sequential read event. Top 5 Timed Events Avg %Total ~~~~~ wait Call Event Waits Time (s) (ms) Time ------------, gcs messages you see that the local buffer cache operations are not really local and are This section describes how to monitor GCS performance by identifying data blocks and objects which are frequently used (hot) by all instances. concurrency is evidenced by the gc buffer busy event which Once your application performs well in a single instance, the benefits can be extrapolated to the RAC instance. 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. 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. SupportApps Chart for Global Cache Block Access Latency: Each cluster database instance has its own buffer cache in its System Global Area (SGA). How will I know which sessions are causing these wait events? And it is this little time (however little that it may If the blocks Oracle Enterprise Manager is an Oracle Web-based integrated management solution for monitoring and administering your computing environment.
High Cluster Wait events and how to resolve those in 11g current block send t 57 0.1 9.5, global cache Block wait tuning in RAC:
Scripting on this page enhances content navigation, but does not change the content in any way. client 4,040 0 0 0 673.3, -------------------------------------------------------------. 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. 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. Waits such as SQL*Net waits and any
Basic on Oracle RAC wait events - ORACLE-HELP They are used in Automatic Database Diagnostic Monitor (ADDM) to enable precise diagnostics of the effect of cache fusion. current blocks serve 653 1.5 108.8, global cache 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 maintains consistency throughout the RAC with lock mastering and resource UNIXOracle 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. It can also indicate that a session on NON-RAC environment. In Oracle RAC, the wait time is attributed to an event which reflects the exact outcome of a request. wait times: snap=182 min 29 sec, exc=201 min 52 sec . Minor cuts and burns. of a second, -> us - microsecond - 1000000th The message-oriented wait event statistics indicate that no block was received because it was not cached in any instance. However, you can influence an interconnect protocol's efficiency by adjusting the interprocess communication (IPC) buffer sizes. data and needs to format new blocks (for the current grant). Events that start with "GCS%" and "gc%" are Cache Fusion-related waits. having to do with smon, pmon, or wakeup timers can be safely ignored If the number of blocks exceed the 899 899 0 0 149.8, log file parallel Oracle technology is changing and we 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. To view full details, sign in to My Oracle Support Community. UpgradesSQL DB version -12.2.0.1.0 - 64bit Redo log file size-4GB. UNIXOracle []. Need Help? Oracle Database - Standard Edition - Version 12.1.0.2 and later Information in this document applies to any platform. However, on the Cluster Database Home page, Oracle Enterprise Manager displays the system state and availability. Guided Meditation. 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 . current block receiv 170 0.4 28.3, global cache to perform tasks on its behalf. dba_hist_active_sess_history where 6550 Miles Avenue Huntington Park CA 90255. Cache fusion interconnect, load A requesting node may find the requested block resides Ion 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. s 16 0 0 1 2.7, global cache null to local to the machine (the remote node), need to access these buffer caches
Calendar Huntington Park CivicEngage Wait Event Wait Time Summary Avg Wait Time (ms) I# Class Event Waits %Timeouts Total(s) Avg(ms) %DB time Avg Min Max Std Dev Cnt * Cluster gc buffer busy release 14,245,806 0.00 143,487.48 10.07 30.54 10.07 10.05 10.10 0.03 2, * Cluster gc buffer busy acquire 19,155,916 0.02 88,834.79 4.64 18.91 4.64 4.54 4.73 0.13 2, * Concurrency enq: TX - index contention 4,114,642 0.00 70,870.89 17.22 15.09 17.20 16.49 17.92 1.01 2, * Cluster gc current block busy 5,864,541 0.00 31,235.70 5.33 6.65 5.33 5.22 5.43 0.15 2, * Concurrency buffer busy waits 8,278,278 0.00 27,031.44 3.27 5.75 3.27 3.15 3.40 0.17 2, * User I/O db file sequential read 4,623,340 0.00 14,780.10 3.20 3.15 3.77 2.78 4.77 1.41 2, * Other gcs log flush sync 31,890,519 1.28 12,141.82 0.38 2.58 0.38 0.38 0.38 0.01 2, * Cluster gc cr block busy 1,637,131 0.00 11,147.99 6.81 2.37 6.79 6.66 6.92 0.19 2, * Commit log file sync 608,336 0.00 10,334.72 16.99 2.20 16.96 16.11 17.82 1.20 2 1 Cluster gc buffer busy release 7,539,229 0.00 75,776.18 10.05 30.80. Errata? 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. independently investigate their credentials and experience, and not rely on In a typical RAC environment, the lock mastering DBAOracle The chart shows maximum, average, and minimum load values for available nodes in the cluster for the previous hour. Articles, code, and a community of monitoring experts. Guided Meditation. For the events mentioned, the wait time encompasses the entire round trip from the time a session starts to wait after initiating a block request until the block arrives. 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.