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  • Sachin Thapa 13:53 on May 28, 2016 Permalink | Reply
    Tags: document, , pdf, rac, rac installation,   

    RAC Installation Step by Step 

    Hi All,

    Please find the below link for RAC installation document for reference.

    (More …)

  • alamgir shaikh 11:03 on November 22, 2014 Permalink | Reply
    Tags: adding, , crs, deletion, node, , rac   

    Adding or Deleting a Node 

    One of the jobs of a DBA is adding and removing nodes from a RAC environment when capacity demands, although you should add a node of a similar spec it is possible to add a node of a higher or lower spec.

    The first stage is to configure the operating system and make sure any necessary drivers are installed, also make sure that the node can see the shared disks available to the existing RAC.

    I am going to presume we have a two RAC environment already setup, and we are going to add a third node.

    Pre-Install Checking

    You used the Cluster Verification utility when installing the RAC environment, the tools check that the node has been properly prepared for a RAC deployment. You can run the command either from the new node or from any of the existing nodes in the cluster (More …)

  • alamgir shaikh 08:56 on November 22, 2014 Permalink | Reply
    Tags: , , , rac, troubleshoot   

    RAC Troubleshooting 

    This is the one section what will be updated frequently as my experience with RAC grows, as RAC has been around for a while most problems can be resolve with a simple google lookup, but a basic understanding on where to look for the problem is required. In this section I will point you where to look for problems, every instance in the cluster has its own alert logs, which is where you would start to look. Alert logs contain startup and shutdown information, nodes joining and leaving the cluster, etc.

    Here is my complete alert file file of my two node RAC starting up.

    The cluster itself has a number of log files that can be examined to gain any insight of occurring problems, the table below describes the information that you may need of the CRS components

    $ORA_CRS_HOME/crs/log contains trace files for the CRS resources
    $ORA_CRS_HOME/crs/init contains trace files for the CRS daemon during startup, a good place to start
    $ORA_CRS_HOME/css/log contains cluster reconfigurations, missed check-ins, connects and disconnects from the client CSS listener. Look here to obtain when reboots occur (More …)
  • alamgir shaikh 08:49 on November 22, 2014 Permalink | Reply
    Tags: cache fusion, , rac   

    Cache Fusion 

    I mentioned above Cache Fusion in my GRD section, here I go into great detail on how it works, I will also provide a number of walk through examples on my RAC system.

    Cache Fusion uses the most efficient communications as possible to limit the amount of traffic used on the interconnect, now you don’t need this level of detail to administer a RAC environment but it sure helps to understand how RAC works when trying to diagnose problems. RAC appears to have one large buffer but this is not the case, in reality the buffer caches of each node remain separate, data blocks are shared through distributed locking and messaging operations. RAC copies data blocks across the interconnect to other instances as it is more efficient than reading the disk, yes memory and networking together are faster than disk I/O.


    The transfer of a data block from instances buffer cache to another instances buffer cache is know as a ping. As mentioned already when an instance requires a data block it sends the request to the lock master to obtain a lock in the desired mode, (More …)

  • alamgir shaikh 08:35 on November 22, 2014 Permalink | Reply
    Tags: global resource directory, GRD, , rac   

    Global Resource Directory (GRD) 

    The RAC environment includes many resources such as multiple versions of data block buffers in buffer caches in different modes, Oracle uses locking and queuing mechanisms to coordinate lock resources, data and interinstance data requests. Resources such as data blocks and locks must be synchronized between nodes as nodes within a cluster acquire and release ownership of them. The synchronization provided by the Global Resource Directory (GRD) maintains a cluster wide concurrency of the resources and in turn ensures the integrity of the shared data. Synchronization is also required for buffer cache management as it is divided into multiple caches, and each instance is responsible for managing its own local version of the buffer cache. Copies of data are exchanged between nodes, this sometimes is referred to as the global cache but in reality each nodes buffer cache is separate and copies of blocks are exchanged through traditional distributed locking mechanism.

    Global Cache Services (GCS) maintain the cache coherency across buffer cache resources and Global Enqueue Services (GES) controls the resource management across the clusters non-buffer cache resources. (More …)

  • alamgir shaikh 08:17 on November 22, 2014 Permalink | Reply
    Tags: , backup and recovery in rac, , rac, rac backup,   

    RAC Backups and Recovery 

    Backups and recovery is very similar to a single instance database. This article covers only the specific issues that surround RAC backups and recovery.

    Backups can be different depending on the the size of the company

    • small company – may use tools such as tar, cpio, rsync
    • medium/large company – Veritas Netbackup, RMAN
    • Enterprise company – SAN mirroring with a backup option like Netbackup or RMAN

    Oracle RAC can use all the above backup technologies, but Oracle prefers you to use RMAN oracle own backup solution.

    Backup Basics

    Oracle backups can be taken hot or cold, a backup will comprise of the following

    • Datafiles
    • Control Files
    • Archive redolog files
    • Parameter files (init.ora or SPFILE) (More …)
  • alamgir shaikh 08:14 on November 22, 2014 Permalink | Reply
    Tags: administration, , rac   

    RAC Administration 

    I am only going to talk about RAC administration

    It is recommended that the spfile (binary parameter file) is shared between all nodes within the cluster, but it is possible that each instance can have its own spfile. The parameters can be grouped into three categories

    Unique parameters These parameters are unique to each instance, examples would be instance_name, thread and undo_tablespace
    Identical parameters Parameters in this category must be the same for each instance, examples would be db_name and control_file
    Neither unique or identical parameters parameters that are not in any of the above, examples would be db_cache_size, large_pool_size, local_listener and gcs_servers_processes

    The main unique parameters that you should know about are

    • instance_name – defines the name of the Oracle instance (default is the value of the oracle_sid variable)
    • instance_number – a unique number for each instance must be greater than 0 but smaller than the max_instance parameter
    • thread – specifies the set of redolog files to be used by the instance
    • undo_tablespace – specifies the name of the undo tablespace to be used by the instance
    • rollback_segments – you should use Automatic Undo Management
    • cluster_interconnects – use if only if Oracle has trouble not picking the correct interconnects (More …)
  • alamgir shaikh 08:05 on November 22, 2014 Permalink | Reply
    Tags: , , , , rac   

    RAC Architecture 

    Oracle Real Application clusters allows multiple instances to access a single database, the instances will be running on multiple nodes. In an standard Oracle configuration a database can only be mounted by one instance but in a RAC environment many instances can access a single database.

    Oracle’s RAC is heavy dependent on a efficient, high reliable high speed private network called the interconnect, make sure when designing a RAC system that you get the best that you can afford. (More …)

  • alamgir shaikh 07:58 on November 22, 2014 Permalink | Reply
    Tags: , , availability, , , high, , rac   

    High Availability and Clustering 

    When you have very critical systems that require to be online 24×7 then you need a HA solution (High Availability), you have to weigh up the risk associated with downtime against the cost of a solution. HA solutions are not cheap and they are not easy to manage. HA solutions need to be thoroughly tested as it may not be tested in the real world for months. I had a solution that run for almost a year before a hardware failure caused a failover, this is when your testing before hand comes into play.

    As I said before HA comes with a price, and there are a number of HA technologies

    • Fault Tolerance – this technology protects you from hardware failures for example redundant PSU, etc
    • Disaster Recovery – this technology protects from operational issues such as a Data Center becoming unavailable
    • Disaster Tolerance – this technology is used to prepare for the (More …)
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