Device Groups

A device group associates two or more save devices as a group. Robot Save allows two different types of device groups: non-AML device groups and Automated Media Library (AML) device groups. This section discusses non-AML device groups. AML device groups are discussed in the AML Maintenance section, later in this User Guide.

Each device in the group must be of the same type and use the same media type and density. You create a device group during system setup using the Device Group Maintenance option. You then specify the device group name on the Save Device Entry panel.

Non-AML device groups are designed to be used with a single system that has multiple drives of the same type configured. With a device group, you can use the drives for the same backup. The first drive writes to a tape until the tape is full. The backup then continues on the second drive while the volume used on the first drive rewinds and unloads.

When a save starts, Robot Save looks at the Backup Set Information panel for the save devices to be used. Robot Save attempts to vary on the first device specified for the set. If that device is not available, Robot Save tries to vary on the next device for the set, and so on. If none of the devices specified for the set are available and if the devices are members of a device group, Robot Save then checks the next device in the device group and attempts to vary it on. When a device is found to be available, Robot Save updates the Backup Set Information panel with the proper device name, sends a message to QSYSOPR, and updates the completion history with the name of the device being used.

After the save is done, all the devices that were used for the save remain on the Backup Set Information panel. Thus, the next time this backup set is run, the save devices listed on the panel may be different from those originally entered.

Robot Save always tries to place the same number of devices on the Backup Set Information panel as originally were specified. For example, suppose you specify TAP03, TAP05, and TAP06 on the Backup Set Information panel. When the save starts, Robot Save checks each of the devices listed for availability. If TAP06 is not available, but TAP08 also is part of the device group and found to be available, the Backup Set Information panel is updated to show TAP03, TAP05, and TAP08. The next save of the backup set will start with TAP03, TAP05, and TAP08 as the devices for the set. If only two devices were found to be available, the panel is updated to show only those two devices. Thus, it is possible to start a save with fewer devices specified for a set than you originally intended.

If none of the devices entered for a set or in the group are available, no changes in devices are made and the save continues, resulting in a “Device Not Ready” message.

Note: Device groups are not supported for restore operations. However, you can change the device to be used for the restore.