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## Cache throttling 

This window shows the statistics of the throttling values that are applied on the host write operations and RUN copy operations throughout the grid. 

Throttling  refers to the intentional slowing of data movement to balance or prioritize system resources in a busy TS7700. Throttling can be applied to host write and inbound copy operations. Throttling of host write and inbound copy operations limits the amount of data movement into a cluster. Throttling is typically done for one of the following reasons: 

GLYPH<SM590000> The amount of unused cache space is low. 

GLYPH<SM590000> The amount of data in cache that is queued for premigration exceeded a threshold. 

Host write operations can also be throttled when RUN copies are being used and it is determined that a throttle is needed to prevent pending RUN copies from changing to the immediate-deferred state. A throttle can be applied to a host write operation for the following reasons: 

GLYPH<SM590000> The amount of unused cache space is low 

GLYPH<SM590000> The amount of data in cache that must be premigrated is high 

GLYPH<SM590000> For RUN copies, an excessive amount of time is needed to complete an immediate copy 

The Cache Throttling graph displays the throttling that is applied to host write operations and to inbound RUN copy operations. The delay represents the time delay, in milliseconds, per 32 KiB of transferred post-compressed data. Each numeric value represents the average of values for all active partitions in the cluster. The following information is shown: 

GLYPH<SM590000> Cluster: The name of the affected cluster. 

GLYPH<SM590000> Copy: The average delay, in milliseconds, that is applied to inbound copy activities. 

GLYPH<SM590000> Write: The average delay, in milliseconds, that is applied to host write operations locally and from remote clusters. 

