Resolution:
In the EMS 5.0, the failsafe is determined by which store you are using for the destination.  If the store you are using is the
type of "sync", then that destination is failsafe. If it is async, then that store is not a failsafe.

For example, Please take a look at stores.conf. It will have the default store entry as:

[$sys.failsafe]
  type=file
  file=sync-msgs.db
  mode=sync
  file_crc=disabled

In the above entry, The mode determines whether messages will be written to the store file synchronously or asynchronously.
Mode is either:
async — the server stores messages in this file using asynchronous I/O calls.
sync — the server stores messages in this file using synchronous I/O calls.
When absent, the default is async.

Suppose if you want to use failsafe destination for the queue named "sample", you have define the queue as
sample store=[$sys.failsafe]

The following is the syntax to define your own store and later can be used with the destinations.

File-Based Stores The format of the file is:
[store_name] # mandatory -- square brackets included
  type = file
  file = name
  [file_crc = true | false]
  [file_minimum = value]
  [file_truncate = value]
  [mode = async | sync]

In the above, mode decides the failsafe or normal.

How to set failsafe destinations after EMS 5.0 using stores.conf file?