Each host in an administrative domain must be assigned one or more of the following Oracle Secure Backup roles:

• Administrative server

  Each administrative domain must have exactly one administrative server. During postinstallation configuration, the administrative server must be configured with complete data regarding the other hosts in the administrative domain, their roles, and their attached tape devices. This configuration information is maintained in a set of configuration files stored on the administrative server.

  The administrative server runs the scheduler, which starts and monitors each backup job. The scheduler also keeps a backup catalog with metadata for all backup and restore operations performed in the administrative domain.

• Media server

  A media server is a host with at least one tape device attached to it. A media server transfers data to or from a volume loaded on one of these tape devices. A media server has at least one attachment to a tape drive or library. It might have attachments to multiple tape libraries and disk pools.

  You specify the attachments between media servers and tape devices during postinstallation configuration of Oracle Secure Backup.

• Client

  The client role is assigned to any host that has access to file-system or database data that can be backed up or restored by Oracle Secure Backup. Any host where Oracle Secure Backup is installed can be a client, including hosts that are also media servers or the administrative server. A network-attached storage device that Oracle Secure Backup accesses through NDMP can also serve the client role.

Each host in the administrative domain must have a unique name that pairs with a unique IP address that is used for TCP/IP communication among the hosts and the media management devices.

In general, the DNS host name can be a good choice for an Oracle Secure Backup host name. Though you can assign a different name to a host, ensure that you specify the IP address as the host object's IP name while configuring Oracle Secure Backup.

Oracle Secure Backup administrative domain uses NDMP to communicate between Compute Hosts and Storage Area Network appliances.

Oracle Secure Backup supports two host access modes: primary access mode and NDMP access mode.

Oracle Secure Backup compute hosts run in primary access mode and have the Oracle Secure Backup software package installed on them. A group of Oracle Secure Backup daemons run in the background that enable communication between the Oracle Secure Backup administrative server, clients, and media servers for performing both file system and RMAN database backups. NDMP access mode is used for communication with SAN appliances.

NDMP access mode is used to communicate with Storage Area Network appliances for backup and restore. Oracle's ZFS Storage Appliance and other third party vendors, such as NetApp and Dell EMC, run their own implementations of NDMP which are supported in Oracle Secure Backup. However, additional parameters specific to the vendor's implementation of NDMP may be required while adding and configuring these devices in the Oracle Secure Backup administrative domain.

A tape drive is a device that reads and writes data on magnetic tapes.

Magnetic tapes are sequential-access storage devices that provide long-term data storage. Unlike disks, the data stored on a tape does not require electricity to sustain it, hence are cost-effective and eco-friendly.

A tape drive uses precision motors to wind magnetic tapes from one reel to another. The tape passes a read/write head as it is wound. These reels are inside a tape cartridge, such as LTO series media, which is the most popular type of drive among Oracle Secure Backup users. A tape is sequential-access storage and since it has a beginning and an end, the tape drive must read through the tape in order to locate the position on the tape where the End of Media is located in order to append to a tape, or locate the position of the written data in the middle of the tape in order to perform a restore.

Tape drives write data in a block format and the block size can influence the backup data transfer rate. Each block is written in a single operation with gaps left between the blocks. The blocking factor can be adjusted to optimize the performance of backups and restores. Typically, large blocking factors are optimum for backing up large files while smaller blocking factors are optimum for backing up numerous small files.

The block size of a block of data is the size of the block in bytes as it was written to tape. All blocks read or written during a given backup or restore operation have the same block size. The blocking factor of a block of data expresses the number of 512-byte records contained in the block. For example, for a site that blocks up a large number of small files, you can set a small blocking factor to match the size of the source data, whereas for sites that back up huge files, you can specify a large blocking factor. The Oracle Secure Backup default blocking factor (128) results in a tape block size of 128*512 bytes or 64 KB.

The maximum blocking factor is an upper limit on the blocking factor that Oracle Secure Backup uses. This limit comes into play particularly during restores, when Oracle Secure Backup must pick an initial block size to use without knowing the actual block size on the tape. The maximum blocking factor limits this initial block size to a value that is acceptable to both the tape device and the underlying operating system.

You can specify the blocking factor and the maximum blocking factor. See "Configuring Tape Drives". The default value for blockingfactor and maxblockingfactor is 128 when Oracle Secure Backup is installed. You can configure domain-wide blocking and maximum blocking factors using the media/blockingfactor and media/maxblockingfactor polices. For more information about the policies, see Oracle Secure Backup Reference.

Things to consider:

• The blockingfactor (block size) must always be less than or equal to the maxblockingfactor.

• The tape drive itself must support the block size settings in use because often tape drives, device drivers, or operating systems have limitations which can supersede other conditions.

• The maxblockingfactor must always be set to be greater than or equal to the largest block you will want to restore.

  When a restore operation starts, Oracle Secure Backup is not aware of the block size that was used to write a given tape. Oracle Secure Backup starts a restore by reading the largest possible block size that is maxblockingfactor. If the blocking factor is too large, Oracle Secure Backup returns an error and displays a message to increase the media/maxblockingfactor policy in obtool.

Information about the tape formats of tape devices supported by Oracle Secure Backup is available at:

http://www.oracle.com/technetwork/products/secure-backup/learnmore/index.html

A tape library is a robotic tape device that operates on SCSI commands.

You can run SCSI commands to move a volume between a storage element and a tape drive. A tape library is often referred to as a medium changer.

A tape library contains one or more tape drives, slots (storage elements or se's) for holding tape cartridges, and provides an automation device to move tapes between drives and storage elements. Figure 1-3 illustrates a tape library containing four tape drives.

Oracle Secure Backup supports tape libraries for managing automatic loading and unloading of volumes to and from the tape drives and storage elements to optimize efficiency.

When a tape library is first configured in Oracle Secure Backup, you must perform an initial forced inventory so that Oracle Secure Backup identifies the contents of the storage elements. Most modern tape libraries require barcode labels on the tapes to perform management operations and for vaulting to other locations. Oracle Secure Backup checks the volume ID of a tape with the barcode to facilitate managing the tape inventory and to identify the tapes required for restore and recycle operations.

After the library and drives are configured, Oracle Secure Backup is configured to automount tapes for backups. Oracle Secure Backup sends commands to the library's robotic arm indicating the tapes to move between the drives and storage elements in order to provide the resources required for a job to backup or restore data. Oracle Secure Backup scans the tape library storage elements to find a suitable volume and uses internal records to optimize tape selection. When you have adequate tapes in the storage elements, Oracle Secure Backup does not require manual loading of tapes to complete backups that span across multiple volumes.

You can configure Oracle Secure Backup to automate the drive cleaning operations. For more information about the policies, see Oracle Secure Backup Reference.

Figure 1-3 shows a tape library with its set of addressable elements:

• Storage Elements (se) are locations where tapes can be stored and available for operations while not in use.

• A data transfer element (DTE) is a tape drive which is used for reading and writing data to and from the tape volume.

• Media Transfer Element (mte) is the robotic arm that moves tape cartridges from the storage elements to and from the tape drives.

• Import Export Element (iee) is a mechanism with a door that an operator uses to transfer tapes in and out of the library. After the door is closed, the robotic arm transfers cartridges to internal slots in the library. If the library is used to move the cartridges around, outside of Oracle Secure Backup, a reinventory is required to update the identification of the storage element contents.

Oracle Secure Backup refers to elements by their abbreviation (mte, se, iee, or dte) followed by the number of the element, for example, se5, iee2, dte1. When multiple elements of a type exist, element numbering starts at 1. When only one element of a type exists, the number can be omitted. Thus, iee1 and iee both refer to the first and only import/export element. If the abbreviation is omitted, then a storage element is assumed. For example, se4 and 4 both refer to the fourth storage element. For some commands, you can specify a range of storage elements, for example, 1-5.

Oracle Secure Backup supports several tape library operations. The following operations are the most basic:

• Inserting and extracting volumes

• Loading and unloading volumes

• Moving volumes

• Importing and exporting volumes

A virtual tape library is one or more large-capacity disk drives partitioned into virtual physical tape volumes. To Oracle Secure Backup the virtual tape library appears to be a physical tape library with at least one volume and at least one tape drive. The volumes and tape drives in the virtual tape library can be configured to match common physical tapes and tape drives.

Backup operations performed to a virtual tape library complete faster than backup operations to actual tape drives, because the underlying storage device is direct access media. But a virtual tape library is not suitable for long time storage, because it has limited storage capacity. If you back up to a virtual tape library, then you can take advantage of its faster backup and then use the volume migration feature of Oracle Secure Backup to migrate the data to tapes at a later point of time.

Because Oracle Secure Backup manages tape drive operations, it must be able to identify the tape drive and determine whether the tape drive is housed in a tape library. Oracle Secure Backup must further determine if a storage element is available for storing a volume while not in use by the tape drive. Thus, each tape device must be uniquely identified within Oracle Secure Backup by a user-defined name.

Oracle Secure Backup distinguishes a tape device and the means by which the tape device connects to a host. To be usable by Oracle Secure Backup, each tape device must have at least one attachment, which describes a data path between a host and the tape device. An attachment usually includes the identity of a host plus an attach point name in Linux or UNIX, a device name in Windows, or a NAS device name. In rare cases, additional information is needed for the attachment definition.