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A quick troubleshooting reference for cluster interconnect performance in Oracle RAC to Identify network and contention issues. a) Check for "gc cr lost blocks" wait event in Automatic Workload Repository (AWR)/sysstats. If found, check for these errors on the NIC: Dropped packets/fragments Buffer overflows Packet reassembly failures or […] To tune the cluster interconnect performance typically the messages buffers size that should transmit between the nodes, the following kernel parameters should set. 256K is fairly adequate. net.core.rmem_default = 262144 net.core.rmem_max = 262144 net.core.wmem_default = 262144 net.core.wmem_max = 262144 -Thanks Geek DBA From the release notes:- https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html-single/6.4_Release_Notes/index.html
As we aware that Oracle didn’t shipped the ASMLIB for RHEL, to progress on that, RHEL has came up with similar modules. Oracle ASMLib Availability and Support Oracle ASM (Automated Storage Management) is a data volume manager for Oracle databases. ASMLib is an optional utility that can be used […] The following sections are key to analyze in the AWR report and identify for RAC global characteristics or load profile. Number of Instances Instance global cache load profile Global cache efficiency percentages GCS-GES workload characteristics Messaging statistics Service Statistics Service Wait class statistics Top segments related to CR and current blocks Number of Instances:- […] You can find Cluster interconnect traffic from 11gR1 using dba_hist_ic_client_stats This view has a column called name which gives you the ability to measure three different types of interconnect traffic. •ipq – Parallel query communications •dlm – Database lock management •cache – Global cache communications break on snap_id skip 1 compute sum of DIFF_RECEIVED_MB on […] Oracle 10gR2 provides an advanced load balancing method to overcome the imbalance of RAC logon’s , especially when there is logon storms, the listeners on the two nodes will simply distribute them evenly across both the nodes. Some case one of the node can be busier than the other . The LBA will calculate how […] Connection Workload management is one of the key aspects when you have RAC instances as you want to distribute the connections to specific nodes/instance or those have less load. Oracle from 10g onwards (9i as well) has two features to provide the connection load balancing Client Side load balancing (also called as connect time load […] Why do we have a Virtual IP (VIP) in Oracle RAC 10g or 11g? Why does it just return a dead connection when its primary node fails? The goal is application availability with the shortest disruption time possible. When a node fails, the VIP associated with it is automatically failed over to some other […] Symptoms: Alert log says WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK! Wait events in Node A: DFS Lock Handle and hanged Wait events in Node B: row cache locks and library cache locks (sessions permitted but very slow) AWR reports says for the interesting period: DFS Lock Handle Background:- DFS Lock […] How to measure the GES Resources (enqueues for RAC ) limit in RAC? Oracle preserves the integrity of the users data during simultaneous use of the same data blocks by different instances using GCS. In addition to data blocks, many other shared resources can be concurrently accessed by end users. Oracle uses a queuing mechanism […] |
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Oracle 23c New Features for DBA's
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