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This technical note gives information on the configuration, setup and tuning of Oracle RMAN 9.x/10.x with Data Domain deduplication storage systems. It is expected that the reader of this paper has a passing knowledge of both Oracle management practices as well as familiarity with backup and recovery techniques for Oracle. A working knowledge of UNIX/Linux and/or Microsoft Windows and the networking components of each is also required. Finally a basic understanding of the setup and management of a Data Domain System is also required.
This perhaps seems like a great deal of background required but will actually serve more as a shortcut to understand some of the shorthand used in this paper. Some theory and background will be presented, but generally only to further explain the recommendations provided. Oracle has now released the next generation database, 11g. As acceptance of this new technology grows, this document will be updated and revised with additional information as necessary. For now, it is recommended that 11g users follow the advice for 10g.
Basic Concepts
A Data Domain System is an appliance which is typically used as a target for backup or archived data. The characteristics that make it good for this include:
- Support for any conventional nearline application through generalized support for Network Attached Storage (NAS) interfaces over Ethernet, a Virtual Tape Library (VTL) interface option over Fibre Channel, and product-specific interfaces such as NetBackup OpenStorage;
- High-speed, inline deduplication using small, variable-sized sequences to identify redundancies;
- Integrated data protection technologies such as RAID-6, postbackup data verification, and periodic validation checks of existing data sets;
- Deduplicated replication to automate disaster recovery (DR).
While a Data Domain appliance offers NAS interfaces, its use as a general purpose file system is generally not recommended because it has not been tuned for small, random-access I/O requests typical of database transactions; it is better tuned for applications that read or write a whole file at a time. On a Windows network, the Data Domain system presents as a network file server accessible via Microsoft’s Common Internet Filesystem (CIFS) protocol. To a UNIX or Linux network, the Data Domain system presents as a network file server accessible via NFS. A single Data Domain system can present both interfaces simultaneously.
Oracle’s Recovery Manager (RMAN) is a built-in tool that allows the Database Administrator (DBA) to easily backup and recover the data in an Oracle database. RMAN handles the coordination required to ensure that transaction integrity is preserved and sufficient information is maintained to recover the database to any appropriate point. RMAN can create backupsets that comprise as much or as little recovery information as the DBA requires but usually includes information from the database datafiles, controlfiles, and redo logfiles. By default RMAN is set up to backup database files to a tape, a disk, a Windows UNC path or UNIX NFS mount path. There are tuning parameters that can be applied for optimum performance and compression.
Additional concepts
Other useful concepts to be aware of prior to getting too far into this paper deal with the details of accessing a Microsoft Windows shared drive, either by mapping a drive a referencing a Universal Naming Convention (UNC) name and setting up and accessing NFS mounts on UNIX/Linux boxes. In either case, sufficient information should be provided during setup to ensure that RMAN has access to the necessary path when it runs. Frequently, user credentials are forgotten during this step so ensure they are correct prior to starting RMAN. Much the same applies to NFS for a UNIX/Linux environment.
Appropriate edits to the /etc/fstab or /etc/vfstab files will be required Finally, credential checking also occurs on the Data Domain system. Ensure that these are setup appropriately.
Oracle environments range from the small, experimental installations to the large production environments that run multi-billion dollar corporations. Because of this large difference in scale, a single recommendation is seldom applicable across all environments. However, some basic best practices for maintaining a reliable Oracle database exist.
Run in archivelog mode
In this mode, Oracle does not delete the redo logfiles that track changes to the database. Instead it “archives” these files to secondary (and sometimes tertiary) locations when Oracle performs its periodic “logswitch”. Without this history of archived logfiles, recovery of an Oracle database to a point prior to an error is significantly constrained.
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