Draft Document for Review February 7, 2020 4:43 pm 8464ch12_Performance.fm The circle on the graph that is shown in Figure 12-8 shows this algorithm in effect. During the  16:15 to 16:45 intervals, the amount of premigrate activity is limited. During the next six  intervals, the premigration activity is zero. After this period of intense host activity and CPU  usage, the premigrate tasks are allowed to start again.  The premigration and premigration throttling value parameters are used to define actions,  which are triggered by the amount of non-premigrated data in the cache. Both values are  applicable to the TS7700T only.  12.6.2 Premigration and premigration throttling values  Premigration Priority threshold (PMPRIOR) Premigration Throttling threshold (PMTHLVL) Figure 12-8 Fast Host Write premigration algorithm When this threshold is crossed, premigration processes start and increase, and the host  throughput tends to decrease from the peak I/O rate. The default value is 1600 GB. The  TS7700T uses various criteria to manage the number of premigration tasks. The TS7700  looks at these criteria every 5 seconds to determine whether more premigration tasks must  be added. Adding a premigration task is based on the following factors, among others: When this threshold is crossed, the host write throttle and copy throttle are started. The  purpose is to slow incoming data to allow the amount of non-premigrated data to be reduced  and not rise above this threshold. The default value is 2000 GB.  The workload creating data (Host I/O, Copy, or remote write) in the TS7700T CP0 is not  subject to throttling for these values.  GLYPH<SM590000> Amount of data that must be premigrated in total  GLYPH<SM590000> Amount of data that must be premigrated per pool GLYPH<SM590000> CPU activity GLYPH<SM590000> Host-compressed write rate 720  IBM TS7700 Release 5.0 Guide