Deactivating unneeded logical partitions

Deactivating unneeded LPs can prove useful for managing how logical paths are established on CPCs in some situations.

The system establishes logical paths only when an LP is activated. Deactivating an LP results in removal of those logical paths associated with the LP. This deactivation can greatly reduce the number of logical paths requested by the system at any given time.

In Figure 1, if all five of the LPs each share all four of the FICON channels and all the LPs are activated, the DS8K would be requested to establish five logical paths for each of the four shared FICON channels (or a total of 20 logical paths). DS8K models support varying numbers of logical paths for FICON channel paths. One such model has a maximum of 1,280 logical paths for a Fiber Channel port in the DS8K. It also has a maximum of 512 logical paths per control unit image of the DS8K. These maximums help to reduce the need for managing logical paths but the maximums can still be exceeded.

For example, if you want to reduce your logical paths by four and you used LP4 and LP5 as test LPs that did not need to be active concurrently, you could reduce the number of logical paths requested by four by not activating either LP4 or LP5. In this case, four LPs (LP1, LP2, LP3, and LP4 or LP5) configured to four shared FICON channels would request a total of 16 logical paths. Later, you could transfer logical paths between LP4 and LP5 by first deactivating one LP to remove its logical paths, then activating the other LP to use the freed logical paths.