Primary DB freezed with waited too long for a row cache enqueue lock

Problem Description
On Oracle database 10.2.0.3.0 Data Guard with Broker configuration whenever there is an attempting to restart the standby in read only, the following error occurs:

ERROR: WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
ORA-12170: TNS:Connect timeout occurred
PING[ARC6]: Error 3113 when pinging standby
ARC6: Attempting destination LOG_ARCHIVE_DEST_2 network reconnect (1089)

The errors occurred in standby database and primary database hangs!

Cause of the Problem
The above error is caused by LGWR process in Oracle Data Guard having RAC environment and it is in fact Oracle bug. The bug number is 7487408.
The bug fires whenever Data Guard is managed by Broker and standby database is shutdown or opened in read only mode. The Primary still tries to ship/send redo streams to standby in SYNC mode and eventually hangs.

Solution of the Problem
- Download the optach 7487408 from oracle support/metalink in order to solve the bug.
- The above bug is fixed in Oracle patchset 10.2.0.5. So you need to upgrade your oracle database to 10.2.0.5.