Resolving errors with SCSI communications

This topic presents a list of actions to identify and resolve communication errors with SCSI devices.

1. Ensure that all SCSI cables from the host to the library are securely connected at both ends.
2. Ensure that each SCSI bus is properly terminated (the bus is terminated at the SCSI host adapter card and at the last drive on the bus).
3. For each SCSI bus, ensure that all devices have a unique SCSI address. No two drives can have the same SCSI ID, and no drive can use the SCSI ID used by the SCSI host adapter.
   Note: Unless an RS/6000 High Availability (HA) configuration is used, the SCSI host adapter is typically set to SCSI ID 7. In an HA configuration, one SCSI host adapter is set to SCSI ID 5, the second SCSI host adapter is set to SCSI ID 6, and SCSI ID 7 is reserved.
4. Ensure that all SCSI host adapters, SCSI terminators, and drives on a single SCSI bus are compatible. For example, if a library contains LVD drives, you must use LVD terminators and LVD SCSI host adapters. Similarly, if the library contains HVD drives, you must use HVD terminators and HVD SCSI host adapters.
5. If there is any Fibre Channel equipment between the host and a SCSI tape drive, perform the following tasks:
   1. Follow steps 1 through 9 in Resolving errors with Fibre Channel communications.
   2. Ensure that the host is configured with the correct Loop ID or AL_PA (see the section about Fibre Channel Addressing in the IBM® TS3500 Tape Library with ALMS Introduction and Planning Guide).
6. Refer to the problem determination procedures in documentation for the device driver that you are using. If you are using the IBM Ultrium Device Drivers, refer to IBM Ultrium Device Drivers Installation and User's Guide. Ensure that the device driver is loaded and that it can communicate with the tape drives:
   1. If the device driver is not loaded, install it.
   2. If the device driver is loaded but cannot communicate with the tape drives, call your IBM service representative.
   3. If the device driver is loaded and can communicate with the tape drives, but the application software cannot communicate with the tape drives, contact the provider of your application software for assistance.
7. Ensure that the SCSI host adapter settings are correct. The following SCSI host adapter settings are necessary:
   • Wide SCSI must be enabled.
   • Disconnect must be allowed.
   • Multiple LUN support must be enabled (for any SCSI host adapter that connects to an Ultrium tape drive which serves as a control path).
8. If the maximum number of cartridges is more than 6 887 for the logical library, or if the logical library has shuttle stations assigned, ensure that the logical library uses LTO Ultrium 4, 3592 E05, or later tape drives as control path drives. In order to support more than 6 887 cartridges, Ultrium 4 control path drives require a minimum code level of 97F0. For logical libraries with shuttle stations assigned, Ultrium 4 control path drives require a minimum code level of A480. Ultrium 5 control path drives require a minimum code level of B170. Perform the following steps to ensure that you have the correct drives and code levels:
   1. Display the control paths using the Drive Assignment page on the Tape Library Specialist web interface. If an older generation tape drive is used as a control path, proceed with the next step.
   2. Follow the instructions in Enabling or disabling a control path in a logical library to disable the older generation tape drive and enable the appropriate drive as the control path.
   3. Reconfigure the host to pick up the device again. Refer to your device driver documentation for additional instructions.