How portal stores the portlet preferences

Question

Where are the portlet preferences saved in case of websphere portal server? Is it some kind of nosql db?

I would expect the portlet preferences are stored in a database. Portal requires a database to store much of the data it holds for its configuration. Portal does not officially support any NoSQL database that I know of, so no, it's likely not a NoSQL DB.

Are there any other things that are stored in this db?

Yes. For example, WCM data is also stored in the database Portal uses.

Does it scale well?

Databases have scaled just fine before the advent of NoSQL. More important is the question of if it will scale well for your environment. That depends on your DB architecture, hardware, etc. In general though, if you're using a supported DB system, in a supported configuration with sufficient hardware, it should scale for your needs. And if doesn't, you can probably contact IBM to ask why.

Is it a db that we can tweak, configure?

It's a DB that your team owns and runs so, it is a DB that you can tweak. Should you though? I certainly wouldn't. Before you decide though, ask yourself two questions:

1) Do you think you can tweak it better than what IBM has already done?

Installation of Portal includes running some SQL database creation scripts that IBM has created and spent time making sure the database performs. Browse through installation instructions and see what all goes into setting up the DB and try to find the scripts that run. Looking at the DB2 versions of the scripts, you'll see they got someone to write those that knew what they were doing with DB2. Not just someone who knew how to define a table with indexes but some deep DB2 administration skills.

2) If your tweaks break your system and you can't recover, will IBM support you and help fix?

This is probably more important than getting optimal performance out of your system. Typically, when a company buys IBM software you get support services in addition to the software itself. As long as you follow IBM's documentation on what's supported, they will help you find and resolve any problem with their product. So when the s**t hits the fan at peak business hours and you're losing revenue, you want to make sure you can get some immediate support if no one from your team has any idea what the hell just happened.