In a previous blog I mentioned that there are effectively two trigger file mechanisms, the PartitionSecuredNotification.XML is the new kid on the block having only been introduced in Enterprise Vault 8. The file has a specific format, and is something that needs to be created by your backup software. The file looks like this:
<?xml version="1.0" encoding="utf-8" ?>
<VendorName>required free form string</VendorName>
<VendorAppType>required free form string</VendorAppType>
<PartitionSecuredDateTime> 2008-03-25T09:30:10+05:30 </PartitionSecuredDateTime>
<VendorTransactionId>optional string</VendorTransactionId> </PartitionSecuredNotification>
You can see here that there is the PartitionSecuredDateTime, which is used by the Enterprise Vault post-processing action (StorageFileWatch). Items prior to this date/time (down to the second, you will notice) are considered to be backed up and 'secure', so they can be turned in to placeholders/stubs/shortcuts as determined by the time of item, and the policy which relate to them.
Software like Symantec NetBackup 7.1 (and higher) use this mechanism, and also some replication software like QUADROtech evNearSync use it as well.