Hi all,
A few days back, I faced a problem where I pg_start_backup('label') was hang in the server forever.
I stopped the process and then used pg_start_backup('label',true) and  it worked.
Now I am trying to investigate why I need to use true as second parameter and read the doc
"There is an optional second parameter of type boolean. If true, it specifies executing pg_start_backup as quickly as possible. This forces an immediate checkpoint which will cause a spike in I/O operations, slowing any concurrently executing queries." 
I tried to regenerate the scenario where  pg_start_backup('label')  hanged and I failed.
Any idea, how can I regenerate that issue to investigate.
I am using Postgresql 9.2.
Thanks.