ISOLATION mode reduces CA Vtape CPU utilization at the expense of slightly higher memory usage. In this mode, CA Vtape allows the operating system to manage the storage footprint. The operating system does not allow the real storage requirements of an address space to grow beyond the parameters you configure for storage isolation. When additional pages are required, the operating system can release pages that have been previously saved. This can result in significant CPU savings because CA Vtape does not need to issue DIV RESET to release saved memory pages.
On heavily loaded online systems with high paging rates and low tape usage, it may be preferable to run CA Vtape in the STANDARD mode. This helps reduce the amount of memory used by CA Vtape. On highly batch-oriented systems, where tape throughput is critical to overall system throughput, consider using ISOLATION mode to reduce CPU cycles needed to manage memory resources.
Note: To use ISOLATION mode, you must correctly configure Storage Isolation within your operating system. To determine the optimum settings for Storage Isolation within your environment, see the chapter "Storage Isolation" in the IBM OS/390 Initialization and Tuning Guide and consult with your systems programmer.
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