Here are some quick notes on how to work with the embedded Derby database that is installed with WebSphere Portal by default.
Run ij.bat from the "embedded" folder (for example, ...WebSphere\AppServer\derby\bin\embedded). The ij utility is a command line client for Derby (kind of like db2cmd). Since this is just a client, you can always install and use a later version of it to get newer features if necessary. For example, I think the show schemas command is only available in later versions of the ij client.
In the ij cmd window, connect to the WPSDB database using a command similar to the following:
To test this connection execute the following query, which should return all the Custom Unique Name records for the entities in the portal:
select * from release.unique_name;
You can refer to Derby documentation for how to use the ij utility.
This technique was learned as a result of the following issue:
A customer had deleted the custom unique name for the portal content root node. This broke everything. When attempting to access the portal, only white screens loaded in the browser. We had to use the following insert statement to manually put the record back in place and recover portal access:
INSERT INTO <RELEASE>.UNIQUE_NAME (UNIQUE_NAME, RES_TYPE, OID, VP_DESC_OID)
VALUES ('wps.content.root',6,X'00000000000000000000000000000000000a' ,X'00000000000000000000d93b44a505010000');
(ensuring that the last value for 'VP_DESC_OID' matched that of the entries that were already there)