IBM TS2340 User Guide - Page 229

3494 Library Emulation Because volume categories are not supported, the following API and mtlib command options cannot be used. Applications and mtlib scripts that use these functions might require changes. v Reserve category mtlib -r option v Release category mtlib -R option v Change a volume category mtlib -C option v Set category attribute mtlib -S option v Assign a category mtlib -k option v Mount from a category mtlib -m -s option Asynchronous Library Operations The 3494 library performs all mount, demount, audit, and eject operations asynchronously and initially returns a request id to the host for the operation. The request id can then be queried at any time to determine if the operation is still pending, completed, or is unknown. SMC libraries perform these operations synchronously and do not support a request id. An application can select to wait for an asynchronous operation to complete by setting the API wait_flg to one or using mtlib without the -n option. The operation is synchronous on both a 3494 and SMC library and no request id is returned to the application. These applications and mtlib scripts do not require any changes. If an application selects to not wait for an asynchronous operation to complete by setting the API wait_flg to zero or using mtlib with the -n option, the operation on an SMC library is still synchronous and request id 0 is returned to the application. Most applications and scripts do not use the return request id to determine when the operation completes and use the no wait option for performance only. For example, using the no wait option on a demount operation so the application can continue while the library is demounting the volume. These applications and mtlib scripts do not require any changes but do take the same amount of time as using the wait option. Applications that use the Query Message ID or mtlib -i option to determine when the return request id operation completes may require changes, such as polling for a mount issued with the no wait option since any request id is always unknown on an SMC library because the operation has already completed. Performance Considerations The performance time of mtlib commands issued to a SCSI 3584 library versus a 3494 vary and some performance times may be significantly higher. The mtlib commands such as -qV and -qI for example that require reading all the slot information from the library also vary in the amount of time it takes for the command to complete. The fewer the number of slots that are in the library, the shorter time it takes to complete the mtlib command and a larger number of slots in the library takes longer. Chapter 9. 3494 Enterprise Tape Library Support 211