Virtual tape cache is a finite amount of storage and virtual tape volumes are eventually migrated to physical tape for different reasons. When jobs request virtual tape data residing on physical tape, a recall must be performed and the volume containing the requested data set must be mounted and the data set migrated back to disk cache. This recall process causes a delay for all jobs requesting a data set which is not in cache. Rocket Virtual Tape Advanced Recall (VTAR) recalls utilize time and resources regardless of which virtual tape device you use. VTAR can pre-stage your migrated virtual tape data and eliminate virtual tape recall wait time.
Even with the variances between manufacturers, an average virtual recall mount time is about 200-300 seconds per recall. Even with a data center daily hit rate of 94%, the time savings can be significant.
Daily Virtual Mounts: 2,000
Recalls at 6%: 120
Seconds Per Recall: 300
10 hours of wait time per day
Workloads that are not run every day will require the most volume recalls since they possess the greater chance of having required tape data sets migrated from cache due to inactivity. The windows for workloads will suffer due to the additional processing time necessary to service the recalls. VTAR eliminates this wait time and allows these periodic cycles to run faster.
By optimizing the recall of virtual tape datasets, VTAR helps you make more effective use of your existing virtual tape cache and can eliminate or postpone expensive virtual tape hardware cache upgrades.
Before recalling a virtual tape dataset, VTAR will first verify that the dataset hasn't already been recalled to cache by another process or previous job. There is no unnecessary overhead.