When files reside on tape, the Tivoli® Storage Manager for Space Management client can order a list of files to recall the files efficiently. Optimized tape recall processing is a feature of the selective recall function.
When files are on tape, it can take a long time to recall a list of files. The requested files can be on different tapes, and the files in the list might not be grouped in the same way as the files are stored on tapes. Tapes can be frequently mounted and unmounted. You can optimize tape access and minimize mounting and unmounting tapes.
To optimize tape recall processing, the dsmrecall command creates ordered lists of files. The command creates one ordered list per tape for files that are stored on tape, and one list for all files that are stored on disk media. Each tape list is ordered to recall the files from tape in the most efficient order.
Optimized tape recall processing provides the following benefits:
The user ID that you use to optimize tape recall processing requires root permission.
Optimized tape recall is a feature of selective recall. Optimized tape recall is not a feature of transparent recall.
Transparent recall processing does not decrease the efficiency of the selective, optimized tape recalls. But the two kinds of recall processing must wait for each other when requesting the same resources. For example, if a transparent recall process requests a tape drive that is being used by an optimized tape recall process, the transparent recall process waits. When the optimized tape recall process is finished with the tape drive, the transparent recall process can use the tape drive.
You can limit the tape drives available for tape optimized processing with the hsmmaxrecalltapedrives option. Limiting the tape drives available for tape optimized processing frees tape drives for other operations like selective recall or migration.