Update 20130619: While patch 6895422 is still available, Oracle has released patch 16087066, which contains the fix from 6895422 along with a fix for bug 13583799. The general recommendation from Oracle now is to use patch 16087066. Also, based on a comment in this MOS post, the 220.127.116.11 EM agent will include this patch and we will no longer need to apply it manually once the next version of the agent is released.
I’ve confirmed that patch 6895422 fixes the TOO_MANY_OPEN_FILES bug encountered with 18.104.22.168.0 agents in an Oracle Enterprise Manager Cloud Control 12c Release 2 environment.
Witness the following metric value graphs of unpatched and patched agents for the “number files open” metric over seven days: