If you want to upset you DBA, and possibly get privileges revoked or at best not be able to ask for any favors, then here's how you can go about that.
Open a SQL editor (SSMS, Toad, Dbeaver, whatever you use to connect to and execute SQL). Connect to the highest level database you have access to. Make sure any kind of autocommit settings are off if this applies.
Now you want to make sure your not going to do anything really damaging like drop tables or something crazy like that - probably you won't have access to do that anyway if the security policies are set up correctly. But you should be able to update some data.
Now open a transaction:
or whatever your specific DB uses to start a transaction.
Now update some tables from within the transaction. It's best to do a whole range of updates and a few inserts just to ensure that table level locks are taken. Do this on a few tables just to be sure.
From within that same transaction, select from all those tables you've altered to verify that the data has changed. And that's it...don't commit the transaction, just leave it open. Before you know it, warnings will go off, alarms will sound, alerts will get sent. Anything using the DB will grind to a halt.
Eventually, a DBA will find that you've caused this and will lose trust and faith in your abilities. Lock the database like this a few times and you'll be put in the corner. Would you lose your job over it? Perhaps....
If you've left a transaction open like this and closed the window with the query, the connection and the transaction might even be left open. Then its up to the DBA to kill the connection and rollback the transaction.
BTW, you should probably ROLLBACK the transaction eventually, perhaps the DBA will ask you to close the trans...that means to roll back the changes you've made so that they go away without actually updating the DB or to COMMIT them which would apply them to the database. In this case, you were just messing with the data so you probably don't really want to commit the changes - they'd be saved permanently!