| e Storage | | | | available for Flash Recovery Area) and then all RMAN |
| There are three distinct options available for an | | | | backups, archive logs, control file auto backups, and |
| installer of an Oracle database. Those available | | | | data file copies will automatically be written to the |
| storage options for database files are File Systems, | | | | specified file system or ASM group. |
| Oracle’s Automatic Storage Management | | | | The Flash Recovery Area can also be tailored to |
| (ASM), or Raw Devices. Each of these storage | | | | meet any database’s needs. It can be large |
| options are defined further in the Installation Guides | | | | enough to keep full, incremental, and archive logs |
| for the particular operating system supported. The | | | | available, as large as the database itself so a |
| Installation Guide should be read to determine how to | | | | complete backup can be done, or small enough to |
| take advantage of the storage option chosen. | | | | just keep archive logs around. Flash Recovery Area |
| File Systems | | | | should be taken advantage of if for nothing else than |
| File Systems are what most DBAs are familiar with | | | | archive redo logs, online redo logs, and control files. |
| and have extensively used. For instance, File Systems | | | | These database structures already take up disk |
| can reside on disks through locally attached disks | | | | space and thus there is no real advantage to not |
| internal to a server, through a Logical Volume | | | | having them within the Flash Recovery Area. |
| Manager (LVM) or Redundant Array of Inexpensive | | | | Moreover, administration of recoveries becomes |
| Disks (RAID) that are on some form of attached | | | | much easier with added features that would not |
| storage device such as a Storage Area Network | | | | normally be available. |
| (SAN). Regardless of the form, these file systems | | | | Integration of Flash Recovery Area |
| are mounted on the host server and when Oracle | | | | Archive log destinations are directly written to the |
| storage is required to create objects or store data | | | | Flash Recovery Area as well as handling online redo |
| Oracle will make use of physical files in some form of | | | | logs. Also, but not shown on the figure, control files |
| predefined directory structure. These physical files | | | | may be stored in the Flash Recovery Area. Backups |
| can either be named by an Oracle DBA or can be | | | | through RMAN are also written to this area. |
| automatically generated by Oracle. The Installation | | | | When configuring database storage, keep in mind |
| Guides provided by Oracle should be consulted for | | | | that the same storage option is not required for |
| your particular operating system to determine how | | | | database or recovery area. File Systems may be |
| to place database files on a File System and how to | | | | used for the database while the Flash Recovery Area |
| follow Oracle’s Flexible Architecture (OFA) to | | | | might be ASM. The only unsupported file type would |
| ensure a reliable and manageable installation. | | | | be raw devices for the Flash Recovery Area, thus |
| Automatic Storage Management (ASM) | | | | another reason to stay away from raw devices. |
| Automatic Storage Management (ASM) is | | | | Oracle Recovery Manager (RMAN) |
| Oracle’s proprietary storage solution for | | | | Oracle Recovery Manager (RMAN) is an Oracle utility |
| Oracle databases that simplifies and removes most | | | | used for backups and restores to an Oracle |
| of the need for traditional disk management tools. A | | | | database. Its use has been widely accepted in the |
| DBA no longer needs to lay out or create database | | | | Oracle community for the ease and efficient method |
| directory structures. ASM handles all underlying disk | | | | with which it can be scheduled, determining backup |
| usage. ASM is able to manage all forms of database | | | | and recovery needs, as well as finding corruption |
| files, provide redundancy, and handle disk corruption | | | | down to the database block level. Under best |
| and failures. ASM is another Oracle instance that | | | | practices, the RMAN environment consists of a |
| communicates with a database instance through | | | | dedicated RMAN instance, which can be directed at |
| Oracle Cluster Synchronization Services (CSS). One or | | | | any number of target database instances for backup |
| more disk devices are allocated to an ASM instance | | | | and recovery needs. |
| and then placed in ASM Disk Groups that in turn are | | | | With the reduction in cost of many disks coupled |
| referenced by the database instance. The Installation | | | | with the simplicity of RMAN and the plain fact that |
| Guide provided by Oracle for your particular operating | | | | many storage vendors are unable to keep pace with |
| system should be read to determine how to install | | | | Oracle technology, Oracle suggests that disk to disk |
| and configure ASM, and then enable use with an | | | | (D2D) backups should be done using the RMAN utility. |
| Oracle database. | | | | The intuitive nature of RMAN and the fact that |
| Raw Devices | | | | RMAN is tightly integrated with the Oracle database |
| Raw devices are nothing more than disks that have | | | | makes this a strategy that should be seriously |
| not been formatted with a file system. When data is | | | | thought of. Plus, many database need to be near real |
| written from Oracle it bypasses the operating | | | | time, which can only be accomplished if disk to disk |
| system file system layer and writes directly to the | | | | backup and restores have been implemented. |
| partition or volume. Because of the complexity to | | | | As noted earlier in this paper, RMAN can use the |
| manage, Oracle does not recommend using raw | | | | Flash Recovery Area to make backups of a target |
| devices. As such, this paper will not present additional | | | | database. This type of backups is inline with |
| information about raw devices and is merely here as | | | | Oracle’s suggested strategy for full and |
| a placeholder to let the reader know they are | | | | incremental backups as well as the keeping of archive |
| available. | | | | and online redo logs. The tight integration of RMAN |
| Flash Recovery Area | | | | with the Oracle kernel and its knowledge of what |
| Oracle’s Flash Recovery Area is an allocated | | | | resides in the Flash Recovery Area, and what needs |
| disk storage location where all backup and recovery | | | | to be backed up or recovered makes it nearly the |
| related files are stored. The Flash Recovery Area can | | | | only choice for optimal management of Oracle |
| be pointed to a File System or Automatic Storage | | | | databases to circumvent disaster. There is no |
| Management (ASM) disk group. All database related | | | | comparison when placed side by side with |
| files required for recovery can be backed up and | | | | user-managed backups and no backup strategy |
| stored in the Flash Recovery Area. These files include | | | | should be considered that does not take advantage |
| the control file, online logs, archive logs, flashback | | | | of RMAN in some form or fashion. For instance, |
| logs, control file auto backups, control file copies, data | | | | RMAN is able to detect block-level corruption that is |
| file copies, and backup pieces. | | | | not available in most alternative backup solutions. |
| The Flash Recovery Area is tightly integrated within | | | | RMAN also contains a catalog that keeps information |
| the Oracle database and is an opportunistic area for | | | | about each backup and aids in the recovery process. |
| performing disk-to-disk backups. With the use of | | | | Conclusion |
| RMAN and the Flash Recovery Area, assuming it has | | | | Availability will often dictate the backup and recovery |
| been allocated enough storage, a powerful | | | | device actually required. However, for database |
| mechanism can be created to provide faster, simpler, | | | | environments that need to be available as much as |
| and automatic recovery of an Oracle database. | | | | possible there is no comparison when confronted |
| Oracle also manages and keeps the Flash Recovery | | | | with the question of tape or disk. |
| Area clean by storing only what is necessary and | | | | Backups in themselves do not necessarily hinder the |
| automatically removing obsolete files that might | | | | availability of a database because an Oracle database |
| would not be needed for a recovery scenario, are | | | | can be continually available while hot backups are |
| redundant copies, or have been backed up to | | | | being done. The real determining factor for disk over |
| another storage device such as tape. | | | | tape is the recovery time. Recovering a database |
| The Installation Guide provided by Oracle for your | | | | from tape can, very conservatively, take in excess |
| particular operating system should consulted to | | | | of 10 times the amount of time it would from disk. |
| determine how to configure the Flash Recovery | | | | Compound this with the time required to reassemble |
| Area. It is as easy as setting two init.ora parameters. | | | | the individual pieces of Oracle, an Oracle database |
| Those being: DB_RECOVERY_FILE_DEST (location | | | | could be down for hours if not days depending on |
| of Flash Recovery Area) and | | | | how large the database is and what pieces are |
| DB_RECOVERY_FILE_DEST_SIZE (Amount of disk | | | | actually going to be restored. |