If you want to set the reserve_policy to "PR_shared" or "PR_exclusive" you will first need to set a PR_key_value. What you set it to will need to be unique, you can set this value to "0x1" for example.
NOTE: Our Purity 2.x implementation of AIX support does not include auto-contingency allegiance (ACA) that is required by AIX. Lacking this support, AIX will not allow a queue depth greater than 1 for Pure LUN's. ACA is supported starting in Purity 3.x.