TAPEDEV configuration parameter

Use the TAPEDEV configuration parameter to specify the device or directory file system to which the ontape utility backs up storage spaces.

onconfig.std value
On UNIX: /dev/tapedev

On Windows: \\.\TAPE0

if not present
On UNIX: /dev/null

On Windows: NUL

Path name
takes effect
For the ontape utility:
  • If it is set to /dev/null on UNIX or NUL on Windows, when the database server is shut down and restarted
  • If it is set to a tape device, when you run the ontape utility
  • When you reset the value dynamically in your onconfig file by running the onmode -wf command.
  • When you reset the value in memory by running the onmode -wm command.

For the onload and onunload utilities: When the database server is shut down and restarted


The ontape utility reads the value of the TAPEDEV parameter at the start of processing. If you set TAPEDEV to /dev/null, you must do it before you start ontape to request the backup. When you set TAPEDEV to /dev/null and request a backup, the database server bypasses the backup but still updates the dbspaces with the new backup time stamps.

You can set the TAPEDEV configuration parameter to STDIO to direct ontape utility back up and restore operations to standard I/O instead of to a device.

The TAPEDEV configuration parameter also specifies the default device to which data is loaded or unloaded when you use the onload or onunload utilities. However, if TAPEDEV is set to STDIO, the onunload utility will not be able to unload data.

If you change the tape device, verify that the TAPEBLK and TAPESIZE configuration parameter values are correct for the new device.

If you specify a TAPEDEV value, ON-Bar ignores the value.

Remote devices (UNIX)

You can perform a storage-space backup across your network to a remote device attached to another host computer on UNIX and Linux platforms. The remote device and the database server computer must have a trusted relationship so that the rsh or the rlogin utility can connect from the database server computer to the remote device computer without asking for password. You can establish a trusted relationship by configuring the /etc/hosts.equiv file, the user's ~/.rhosts files, or any equivalent mechanism for your system on the remote device computer. If you want to use a different utility to handle the remote session than the default utility used by your platform, you can set the DBREMOTECMD environment variable to the specific utility that you want to use.

Symbolic links to remote devices (UNIX)

The TAPEDEV configuration parameter can be a symbolic link, enabling you to switch between tape devices without changing the path name that the TAPEDEV configuration parameter specifies.

Use the following syntax to specify a tape device attached to another host computer:
The following example specifies a tape device on the host computer kyoto:

Rewinding tape devices before opening and on closing

The tape device that The TAPEDEV configuration parameter specifies must perform a rewind before it opens and when it closes. The database server requires this action because of a series of checks that it performs before it writes to a tape.

When the database server attempts to write to any tape other than the first tape in a multivolume dbspace or logical-log backup, the database server first reads the tape header to make sure that the tape is available for use. Then the device is closed and reopened. The database server assumes the tape was rewound when it closed, and the database server begins to write.

Whenever the database server attempts to read a tape, it first reads the header and looks for the correct information. The database server does not find the correct header information at the start of the tape if the tape device did not rewind when it closed during the write process.