Does applying Performance Service Levels in Active IQ Unified Manager actually change anything on the storage array side, i.e. applying QoS to volumes/LUNs or does it merely tag the volume/LUN in AIQUM for its analysis or the workload? The documentation is anything but forthcoming on this point.
No, It does not. AIUM/OCUM only provides "QoS policy group" analysis and recommendations. The QoS can only be applied via System Manager/CLI or using automation tool called "WFA". AIUM will only display the pre-defined QoS policies that you have defined on the ONTAP itself. Yes, you can create user-defined policy and attach it to objects for viewing their IOPS/MBs performance to get an idea on how they are actually doing. However to stop them (ex-vol/lun) from consuming resources, you will need to apply it on the OTNAP itself.
Active IQ Unified Manager 9.7 inherits the Service Level Objective Management feature formerly available in NSLM - NetApp Service Level Manager.
With this a user can *actively* provision resources, including an AQoS (adaptive QoS) and/or an efficiency policy.
Also assigning AQoS policies to pre-existing workloads (=volumes and LUNs) is possible, but should be evaluated carefully. Please review the section "Provisioning and managing workloads" in the AIQUM9.7 online help (Link to Offline Help for your reference).
In short - if you assign either a Performance Service Level, or a Storage Efficiency Policy in the AIQUM UI, it will go and alter the volume configuration to the respective AQoS and/or efficiency policy.
Be *very* careful with the blue button that reads "Assign System-Recommended PSLs" - it has a warning sign for a reason. It will go out and configure *all* volumes and LUNs with the AQoS policy AIQUM analyzed to be the best fit and override any pre-existing QoS settings for the volumes.
I deem the PSL-based provisioning and management to be a very strong feature. But you need to get your head around it as it may fundamentally change the way how you may have provisioned resources in the past.