First, cache is never pre allocated, unless you use Perma Cache. There are however limits to WP tracks on volumes and system. At one point in time there was also a WP limit per DA, but even when that was in place, it was rarely invoked.
Perma Cache is a feature where you can reserve cache space for specific address ranges of a given volume. Then that space in cache cannot be used by any other volume. It does not change WP limits however.
The symcfg list -v output shows Max # of DA Write Pending Slots to be a value of zero. This is an issue with Solutions Enabler/microcode defect. Upgraded from Solutions Enabler 6.5. This parameter is obsolete and will be removed in a future version of Solutions Enabler. If using Ucode 5773 and below, Problem will be corrected with Solutions Enabler 7.2.0 and up. As a workaround, EMC Engineering recommends using "Max # of System Write Pending Slots" instead.