Cautions and restrictions for Virtual Partition Manager

Impact on host performance
Creating and changing cache logical partitions can significantly degrade host performance and should only be performed during the initial installation and setup of the storage system or during maintenance. If you must perform these changes on a production machine, use Performance Monitor to verify that the write pending rate and sidefile occupancy rate of the CLPR and CLPR0 satisfy the following formulas on all MP unit:
- For CLPR with decreased cache capacity
```
Write pending rate x cache capacity before operation / 
cache capacity after operation < 30%
```
```
Sidefile occupancy rate x cache capacity before operation / 
cache capacity after operation < sleep wait threshold x 50%
```
- For CLPR with increased cache capacity
```
Sidefile occupancy rate < sleep wait threshold x 50%
```
When you move resources in CLPRs, make sure that the writing pending rates of the MP unit for each CLPR are less than 50 percent at both the source and the destination. The process for changing the CLPR settings will be suspended until the write pending rates of each MP unit become less than 50 percent.
Duration of cache partition operations
Adding or changing CLPR definitions or configurations can take hours to complete.

Interoperability restrictions for cache partitioning

Application	Behaviors
ShadowImage/ ShadowImage for Mainframe	You cannot use ShadowImage or ShadowImage for Mainframe Quick Restore functions that affect multiple CLPRs.
Volume Migration	You cannot use Volume Migration when it affects multiple CLPRs.
Universal Replicator	Universal Replicator data volumes and journal volumes can belong to different CLPRs. All journal volumes in the same journal must belong to the same CLPR. If not, an error occurs.