Why would "adop phase=prepare" spawn a conc request which dies with out of memory after taking 75G?

We're on Solaris 11 with EBS 12.2.5 and the required ETCC patches.

> adop phase=prepare

This submits a concurrent request entitled "Online Patching In Progress" to the Standard Manager.  Before this request begins running, my 148G system has at least 65G RAM free.  WIthin an hour of the request the top command shows we're down to less than 4G of free memory.

applmgr@cdroad01:/homes/applmgr::prstat -Z 1 1

   PID USERNAME  SIZE   RSS STATE   PRI NICE      TIME  CPU PROCESS/NLWP

19034 applmgr    72G   71G cpu12    30    0   0:36:51 3.9% perl/1

12668 root      704M  626M sleep    59    0   0:12:17 0.1% java/132

   575 applmgr  2190M  719M sleep    59    0   0:09:45 0.1% java/72

That perl program taking 71G of memory is this adop prepare process: