Configuration parameters

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The operating parameters for the tape drive and device driver are set and changed by configuration parameters. The installation defaults are provided for all parameters initially. The AIX® smit command is used to set these parameters when a device is configured or to change these parameters. The AIX chdev command is used to change the configuration parameters.

The configuration parameters are used to set the operating mode of the tape drive and device driver when a device is opened. These parameters can be queried by an application. Some parameters can be temporarily changed during the open subroutine by an application. But, they are always restored to the configuration values when a device is closed. The configuration parameters are
  • Alternate Pathing
  • Autoloading
  • Emulate autoloader (359x devices only)
  • Block size
  • Buffered mode (359x devices only)
  • Compression
  • Fail degraded media (359x devices only)
  • Logical write protect (359x devices only)
  • Logging
  • Maximum size of the log file
  • New logical name
  • Read error recovery time (359x devices only)
  • Record space mode
  • Reservation key
  • Reservation support
  • Reservation type
  • Retain reservation
  • Rewind immediate
  • System encryption
  • System encryption for Write Commands
  • Trailer labels
  • SCSI status busy retry
  • iostat support for tape

Alternate pathing

This parameter enables or disables the path failover support when a device is configured. See Data Path failover and load balancing support for tape drives for a description of the path failover and failover support.

The installation default is no (path failover is not enabled).

Autoloading

This parameter enables the autoloading feature of the device driver. It is used with the autoloading capability of the autoloader, ACF, ACL, or CSL installed on the tape device.

Note: The autoloading feature is not supported on the IBM® 3584 UltraScalable tape library and the IBM 3583 Ultrium Scalable tape library with more than one IBM 3580 Ultrium tape drive installed.
Note: The autoloading feature is supported only on the following device types and configurations:
  • IBM 3490E Models C11, C22, E01, E11, F01, and F11
  • IBM Enterprise Tape System 3590, Models B11, E11, and H11
  • IBM Magstar® MP 3570 Models B01, C01, B11, and C11
  • IBM Magstar MP 3570 Models B02, B12, C02, and C12 (configured in split mode only)
  • IBM 7332 (all models)
Do not enable autoloading if one of the following conditions is true.
  • The device is used by an application that provides library medium changer support for the IBM 3581 or IBM 3583.
  • The device is installed in a 3494 Enterprise Tape Library.
  • The device is used by an application with stack loader support.
  • The application is MKSYSB.
  • The tapes that are read were not written with the autoloading feature.

Tapes that are created with AUTOLOAD=YES are not readable in configurations without Atape autoload enabled, or on other UNIX operating systems, or on device types/models that are different from the backup device type/model.

If the parameter is set to On, then the tape stacker acts as one large virtual tape. During a read, write, or forward space file operation, no end of tape is detected by the application. When the end of tape is reached, the device driver automatically rewinds and unloads the tape, then loads the next tape. Then, it continues reading or writing the next tape. The following conditions are required to use this feature:
  • The autoloading parameter must be set to On.
  • The cartridge stacker must be loaded with one or more tapes.
  • The ACF, ACL, or CSL must be set to Automatic, System, or Random mode.

This feature allows multivolume backups (with commands such as tar) without prompting for a volume change.

The installation default is Off (no autoloading).

Emulate autoloader

This parameter controls how the device driver operates when the ACF on the IBM Enterprise Tape System 3590, the IBM Magstar MP tape device, or the IBM 3490E Model Fxx is set to Random mode. If this parameter is set to On and the ACF is in Random mode, the device driver emulates an autoloading tape drive. When an unload command is sent to the device driver to unload a tape, the tape is unloaded, returned to the magazine, and the next tape in the magazine is loaded automatically into the tape drive. If this parameter is set to Off, the normal unload operation occurs, and the tape remains in the drive.

The emulate autoloader parameter can be used for legacy applications that are written for the IBM 3490E Automated Cartridge Loader (ACL) when the IBM Enterprise Tape System 3590, the IBM Magstar MP 3570, or the IBM 3490 Model F autoloader is set to Random mode. This parameter eliminates the need to reconfigure the autoloader of the device Random or Automatic operation.

The installation default is Off (do not emulate autoloader).
Note: On IBM Magstar MP 3570 Models B02, C02, and C12, this feature is supported only when the two drives are configured in Split mode, or in Base mode with one drive that is configured and available to AIX. This feature does not work in Base mode if both drives are in the available state to AIX.

Block size

This parameter specifies the block size that is used for read and write operations. A value of zero is the variable block size. Any other value is a fixed block size.

The installation default is zero (use variable length) except for the IBM 7332 4-mm Tape Cartridge Autoloader, for which the default is a fixed block size of 1024 bytes.

Buffered mode

When a write command is processed, the data is either stored directly on the physical tape or buffered in the tape device. Buffering can increase the device performance.

The installation default is On (use Buffered mode).

Compression

Hardware compression is implemented in the device hardware. This parameter turns the compression feature On and Off. If compression is enabled, then the effective performance can increase based on the compressibility of the data.

The installation default is On (use compression).

Fail degraded media

This parameter controls whether the device driver fails a tape operation when degraded media is detected by the IBM Enterprise Tape System 3590. If a tape is loaded and the IBM 3590 cannot read the positioning information from the tape, the device driver is notified when the first command is sent to the tape drive. If this parameter is set to On, the device fails the command and returns a media error to the application. If this parameter is set to Off, the device driver does not fail the command.

Degraded media is a correctable condition that prevents the IBM Enterprise Tape System 3590 from running high speed Locate operations. A Locate command can take over 20 minutes, depending on the wanted position and the amount of data on the tape. This parameter is intended for use by real-time applications that cannot tolerate long Locate commands.

The installation default is Off (do not fail the tape operation if degraded media is detected).

Logging

This parameter turns the volume information logging on and off. If logging is set to On, the statistical information about the device and media is saved in a log file when a tape is unloaded. If logging is set to Off, the information is not saved. This parameter has no effect on error logging because error logging is always enabled. For information, refer to Device and volume information logging.

The installation default is Off (no logging).

Maximum size of the log file

This parameter specifies the number of entries that are made before the log file starts to wrap. Each entry is approximately 2 KB (2048 bytes). After the log file starts to wrap, the number of entries stays constant. Each time a new entry is made, the oldest entry is overlaid. For information, refer to Device and volume information logging.

The installation default is 500.

New logical name

Setting this parameter changes the logical name of the device to a new name as specified. After the logical name is changed, the new logical name parameter is cleared. For information, refer to Persistent Naming Support.

There is no installation default value for this parameter.

Read error recovery time

This parameter controls the read error recovery time for the IBM Enterprise Tape System 3590. If this parameter is set to On, the recovery time for read errors is limited to a maximum of 5 seconds. If this parameter is set to Off, full recovery is used by the device and can take up to 10 minutes. This parameter is intended for use by real-time applications that cannot tolerate long delays when data is read from the tape.

The installation default is Off (do not limit the read error recovery time).

Record space mode

This parameter specifies how the device driver operates when a forward or backward space record operation encounters a filemark. The two modes of operation are SCSI and AIX.

The SCSI mode is the default mode of operation. When a forward or backward space record operation is issued to the driver and a filemark is encountered, the device driver returns -1 and the errno variable is set to input/output error (EIO). The tape is left positioned after the filemark (the end-of-tape side of the filemark on the forward space and the beginning-of-tape side of the filemark on the backward space).

The AIX mode returns the same EIO errno value as the SCSI mode when a filemark is encountered except that the tape is left positioned before the filemark (the beginning-of-tape side of the filemark on the forward space and the end-of-tape side of the filemark on the backward space).

The installation default is SCSI mode.

Reservation key

This parameter specifies the SCSI Persistent Reservation key that is used by the device driver when either the Reservation Type parameter is SCSI Persistent Reserve and the Alternate Pathing parameter is set to no or when the Alternate Pathing parameter is set to Yes.

The default for this attribute is blank (NULL).

If the Reservation Key parameter is specified as blank (NULL), then the device driver uses an internal unique key for all devices on the host they are configured on. Another AIX host that shares devices also have an internal unique key for all devices if the Reservation Key parameter was blank (NULL).

If the default is not used, then the Reservation Key value can be specified as either a 1-8 character ASCII alphanumeric key or a 1-16 hexadecimal key that has the format 0xkey. If fewer than 8 characters are used for an ASCII key (such as host1), the remaining characters are set to 0x00 (NULL). If less than a 16 hexadecimal key is used, the remaining bytes are set to 0x00.
Note: When a Reservation Key is specified on each host that shares a device, the key must be unique to each host.

Reservation support

The parameter of reserve_support indicates that the Atape driver manages the reservation for the tape device when it is enabled. Atape reserves the tape device in open and releases it in close, and maintains the reservation in error recovery procedure (ERP).

Note: For the medium changer, this parameter is not applied when the Alternate Pathing (path failover) parameter is set to Yes. The device driver forces the setup to be disabled and the medium changer is not reserved in open when the Alternate Pathing parameter is set to Yes.

The installation default is Yes.

Reservation type

This parameter specifies the SCSI Reservation type that is used by the device driver, either a SCSI Reserve 6 command or a SCSI Persistent Reserve command.
Note: This parameter is not used if the Alternate Pathing (path failover) parameter is set to Yes. The device driver uses SCSI Persistent Reserve when the Alternate Pathing parameter is set to Yes.

The installation default is SCSI Reserve 6.

Retain reservation

When this parameter is set to 1, the device driver does not release the device reservation when the device is closed for the current open. Any subsequent opens and closes until the STIOCSETP IOCTL is issued with retain_reservation parameter set to 0. The device driver still reserves the device on open to make sure that the previous reservation is still valid.

The installation default is Off (the reservation is released in close).

Rewind immediate

This parameter turns the immediate bit On and Off in rewind commands. If it is set to On, the rewind tape operation runs faster. However, the next command takes a long time to finish unless the rewind operation is physically complete. Setting this parameter reduces the amount of time that it takes to close a device for a Rewind on Close special file.

The installation default is Off (no rewind immediate) except for the IBM 7332 4-mm Tape Cartridge Autoloader, for which the default is On (rewind immediate).

System encryption

This parameter specifies whether System-Managed Encryption must be used. For information, refer to System-managed encryption.

The installation default is No.

System encryption for Write commands

This parameter controls if System-Managed Encryption is used for Write commands. For information, refer to System-managed encryption.

The installation default is Custom.

Trailer labels

If this parameter is set to On, then writing a record past the early warning mark on the tape is allowed. The first write operation to detect EOM fails, and the errno variable is set to ENOSPC. No data is written during the operation. All subsequent write operations are allowed to continue until the physical end of the volume is reached and EIO is returned.

This parameter can also be selected by using one of three device special files that allow trailer-label processing. The special files are rmtx.40, rmtx.41, and rmtx.60, where x is the name of the device (for example, rmt0.40).

The installation default is Off (no trailer labels).

SCSI status busy retry

Atape retries the SCSI command fail due to the SCSI status Busy when the parameter of busy_retry is set to On. Otherwise, Atape fails the SCSI command if it is set to Off.

The installation default is Off.

iostat support for tape

The iostat command is used to monitor system input/output (I/O) devices. To work this system command for tape, Atape reports input and output statistics on each tape drive.

The installation default is On.