Oracle performance issue when fetching BLOBs

Guys, I just came back from a customer who has a problem, they are keeping a large BLOB which contains serialized java classes per each subscriber in their system.

Usually Oracle fetches the BLOB fast enough for them to deliver within their performance goals, but once in a while (about 0.5% of the cases) the fetch takes longer times and causing them delays that are unacceptable.

I have two questions for you:

(1) is that right that Oracle is not a "real-time" system, therefore it will not guarantee response time? why does Oracle sometime takes more time than average to process a query, and can this be optimized by configuration??

(2) does it make sense to store the data not in the database (e.g. file-system, LDAP, SAN, gFS, ...) given that all we need is to be able to lock, read and write the data.

What do you think??

Developer