Very Computer

I am currently working on a project that requires calling external
procedures (written in C,C++ or Java) from a database whenever the
updates or changes occurs in the database table. It is important that
the database server continues serves other incoming requests that
would make calls (or cause triggers) to external procedures.

I am seeking the answers to the following questions:

1. What database servers allows triggers or call to external
procedures in C,
   C++ and Java languages?
2. Is it possible to pass the data (e.g a row or several rows in the
table that is being changed) to the external procedure.
3. When the external procedure is executed:
   - will database server blocks other requests until the execution
     of the external procedure is finished
                           (or)
   - will it just call the external procedure and continue to serve
the other
     requests

Any help, information and pointers to answers would be a great help
for me.

many thanks in advance,
judge