I use openrdf-sesame memoryStore(persist) and native store as my data stores.
Whats the standard/recommended way of backup/restore my datastores?
Is there any supported api?
I run sesame standalone server.
You can quite easily create something yourself, just by using RepositoryConnection.export. However, there are also a few ready-made (commandline) tools available, for example this simple sesame-backup tool (disclaimer: I developed that). Download, install, and stick in a cronjob to have it make regular scheduled backups.