VERITAS Volume Replicator in an Oracle Environment

VERITAS Volume Replicator in an Oracle Environment

Introduction Remote replication of online disks and volumes is emerging as the technique of choice for protecting enterprise data against disasters. VERITAS Software Corporation, the data availability company and the world s leading provider of storage management software, offers VERITAS Volume Replicator, an elegant, flexible, storage independent solution for disaster recovery when currency and availability of data are paramount. Oracle Corporation, the leading supplier of relational database technology for the enterprise, also recognizes the importance of disaster recovery, and has instituted an audited testing program to verify that Oracle technology operates correctly with other vendors replication products. VERITAS Volume Replicator is the first replication solution to successfully complete the Oracle Storage Compatibility Program (OSCP) disaster recoverability tests. This paper briefly discusses some of the key concepts of data replication, explains some of the features and strengths of the VERITAS Volume Replicator, and describes how it can be used to achieve robust disaster recoverability in conjunction with Oracle s database technology. 2

The Challenge: Continuously Accessible, Trustworthy Data Companies today rely to an unprecedented extent on online, frequently accessed, constantly changing databases to run their businesses. Unplanned events that inhibit the availability of this data can seriously damage business operations. Additionally, any permanent data loss (from natural disaster or any other source) will likely have serious negative consequences for the continued viability of a business, especially in an Oracle environment. Therefore, when disaster strikes, companies must be prepared to eliminate or minimize data loss, and recover quickly with useable data. Replication technology allows IT organizations to deliver both current data and immediate recoverability in the event of a disaster. Even with a very well executed backup strategy, restoring from tape usually results in several hours of lost data. For many Oracle environments this kind of data loss is unacceptable. Real-time replication not only minimizes or eliminates data loss, but also enables rapid recovery when compared to conventional bulk data transfer from sequential media. The replica data is available and ready for use on disk at a disaster-safe location. VERITAS Volume Replication The key element for any replication based disaster recovery strategy is an uncompromised data mirror at a disaster safe location. Depending on business requirements, this could be across campus, across town, or across continents. In addition to having data at a disaster safe location, the ideal replication solution would ensure that the replica volumes are current (fully up to date), complete (including all applications, logs, configuration data, etc.), and recoverable (free from errors and consistent from an Oracle standpoint). VERITAS Volume Replicator is the optimal replication solution to deliver a current, complete, and recoverable Oracle environment at a remote location. Current: When operating in synchronous mode, VERITAS Volume Replicator guarantees a perfect bit-for-bit image without missing a single application write transaction. This obviously produces the highest level of data currency. For sites that can tolerate a minimal delay (usually measured in seconds or milliseconds) asynchronous replication delivers a high level of data currency, while eliminating possible performance bottlenecks associated with network round trip latencies seen in full synchronous implementations. With VERITAS Volume Replicator, IT administrators can select either synchronous or asynchronous replication depending on their requirements. Complete: VERITAS Volume Replicator replicates entire volume contents (including all applications, logs, configuration data etc.) so administrators can feel confident that a replica of the entire Oracle environment is available to stand in for the primary at all times. Recoverable: Having a corrupt or unrecoverable data set at a remote site is of little benefit when disaster strikes. VERITAS Volume Replicator s comprehensive volume group replication ensures maximum data integrity and consistency. Exposure associated with an inconsistent replica volume is eliminated. In addition to providing current, complete, and recoverable data, VERITAS Volume Replicator runs on all storage hardware platforms, eliminating storage vendor restrictions and lock-in. VERITAS Volume Replicator also scales to support up to 32 hosts for one-to-many scenarios, and easily accommodates many-to-one configurations for centralized protection of multiple production servers. Since VERITAS Volume Replicator replicates volume contents, VERITAS Foundation features are available for replicated volumes at both primary and secondary sites. These include availability enhancements such as mirroring, general purpose performance enhancements, such as data striping, and database specific performance enhancements, such as quick I/O for databases. 3

Replicating Oracle Databases with VERITAS Volume Replicator Based on VERITAS Volume Manager, the de facto standard for online disk management, VERITAS Volume Replicator provides an intuitive, flexible and completely compatible solution for replicating Oracle environments. A brief overview of the steps required to set up VERITAS Volume Replicator will demonstrate why it is the ideal solution for maintaining remote copies of mission critical Oracle environments. First, an Oracle instance is created on volumes managed by VERITAS Volume Manager, and volumes at the primary site requiring replication are identified. The corresponding target volumes at the secondary location are also created (the volume geometry does not need to match). Second, a persistent volume replication log is set up to track write updates for asynchronous or dynamic synchronous modes to maintain consistency at the secondary. A replicated volume group containing all interrelated volumes is then created as the unit of replication. This ensures that consistency is maintained within and among volumes comprising the entire Oracle instance. Next, the secondary must be initialized in one of two ways: Over the wire by sending all data over the network, or via backup and restore (especially for very large databases). Both operations can be performed while Oracle is online and operating normally. Finally, the administrator defines the desired replication mode (asynchronous or synchronous) and activates the replication link, or r-link, between the two hosts. Once replication policies have been set, replication is automatic, requiring no system administrator intervention until an exceptional event such as a site disaster actually occurs. During replication, writes to Volume Manager by Oracle are then transmitted over the IP network to the remote host. In synchronous mode, the remote host must acknowledge the receipt of each write before allowing the write operation to complete, keeping the primary and secondary fully current. In asynchronous mode, writes are logged (in order) to be replicated as bandwidth allows. Operation in asynchronous mode does not require acknowledgement from the remote host before the write operation is completed, likely increasing Oracle response time at the primary. Administrator defined high watermarks available in VERITAS Volume Replicator prevent the secondary nodes from falling too far behind the source when operating in asynchronous mode. If a disaster occurs at the primary site, the secondary replicated volumes may be promoted to primary status and Oracle s automated recovery procedure is invoked to restore the database image. SITE 1 APPLICATION FILE SYSTEM SITE 2 APPLICATION FILE SYSTEM ACTIVE I/O MANAGER REPLICATOR R-LINK IP NETWORK R-LINK MANAGER REPLICATOR 127GB LOG Replicated Volume Group Replicated Volume Group 127GB LOG 500GB 500GB 50GB 50GB VERITAS Volume Replicator fully integrates with VERITAS Volume Manager to replicate volume groups over any IP network to a disaster safe location. 4

Summary In today s competitive environment many companies running Oracle have data currency and availability requirements for their disaster recovery planning that only a real-time replication technology can provide. The Oracle Storage Compatibility Program (OSCP) includes a stringent battery of tests to verify that replication products maintain transactional recovery of Oracle databases at remote sites. As the first solution to successfully complete these tests and attain OSCP approval, VERITAS Volume Replicator delivers a critical component for a robust business continuity strategy in any mission critical Oracle environment. For more information on VERITAS Volume Replicator and other VERITAS solutions that complement Oracle environments, please visit the VERITAS web page at www.veritas.com. 5

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