to many locks held

Hi everybody,

In recent days, we have seen many processes in reaching the lock held
5000. At that time my machine will become sluggish and no response from
the database. I tried to change configuration parameters, but have not
found anything satisfactory. further in meeting log messages like the
following:
COTidleERROR: out of memory
COTidleDETAIL: Can not enlarge string buffer container containing 0
bytes by 1476395004 more bytes.
COTidleLOG: incomplete message from client
COTUPDATE waitingLOG: process 20761 still waiting for ShareLock on
transaction 10,580,510 1664,674 ms after

My machine is on linux postgres version 9.2.2, and the following settings:

memory ram: 128 GB
cores: 32

max_connections: 900
shared_buffers = 2048MB
work_mem = 1024MB
maintenance_work_mem = 1024MB
temp_buffers =  512MB
checkpoint_segments = 103

regrads