Resolution:
Description:
============
You could notice the dropping of EMS inbound message rate from time to time in the following scenarios:

1). Messages are written to datastore configured to use async mode.

2). The number of pending messages is increasing, for example, when there are fast producers and slow consumers and  EMS needs to keep writing to the store.

Causes:
===========
When messages are written to async store, they are first cached by the OS in memory.  When they are later forced to be written to disk by the OS, the write call by EMS is blocked.  Since EMS uses an I/O thread to write messages to the store file, this blocking leads to dropping of the message inbound rate.

When store uses sync mode, there is no caching or forced writing.  Each EMS write call only returns after the message is written to disk.  If file_minimum is configured on the store, you will notice that the inbound message rate only drops when the pending message size is near file_minimum.

Resolution
========
OS flushing configuration can be changed. For example, on Linux refer to:

http://www.westnet.com/~gsmith/content/linux-pdflush.htm

Consult your OS vendor for more information.

Environment:
===========
All

Keywords:
=========
flushing cache inbound message rate async store

Dropping of message inbound rate due to increase in the number of pending messages.