Caching in IFS

Question

As an application developer I would like
to understand what all iFS caches. What
happens in a load balanced scenario?
Let us say I have two iFS applications
that hit the same iFS database. If iFS
does any caching, does it take care of
refreshing the cache when one instance
of the application changes data (user
profile, ACLs etc).
I would like to know what gets cached
in iFS.
null

Answer 1

Allow me to clarify a few things.
You can think of an iFS service as the "black box" that handles all the communication between the iFS server software (Java) and the database. An iFS service is "pointed to" a specific schema in a specific database instance (recall that you get to choose these with the iFS Configuration Assistant).
The iFS service manages the caches, connection pools, etc., hiding all the details from iFS clients. (iFS clients are you, the developer who uses the published API, as well as each protocol server and application, such as FTP and the WebUI.)
In iFS 1.0 and 1.1, each iFS application (like ServerManager or SMB) has a single iFS service -- that is, each JVM has a single iFS service (note that this is not a restriction, it's just the default configuration; if you really wanted to, you could have multiple iFS services in a single JVM).
Each iFS service has an associated configuration file, which you can find in the $ORACLE_HOME/ifs/settings/oracle/ifs/server/properties directory. Note that just because a service configuration file is present in the afforementioned directory does not mean that that service is up and running; the service properties file is just one of the services that you COULD start up.
Each iFS service manages a set of iFS sessions (you create a session when you get a new LibrarySession instance using the LibraryService.connect method).
When you start adding middle tiers, the pattern still holds. For instance, if you have FTPServer1 on MachineA, that's one iFS service. If you add FTPServer2 on the same machine (MachineA), that's another iFS service. If you add FTPServer3 on MachineB (a second computer), that's just another service. The visibility rules described above apply in the same way in all of these cases. All you need is a connection to the database, which is provided by the Oracle Client (JDBC over Net8).
Finally, let me just say that synchronizing these caches is non trivial -- iFS is an extremely powerful distributed application. (I had to get that in there.)