What are disadvantages of pl-sql?

Java

If you're just running Oracle databases, there are no major disadvantages to using PL/SQL as long as you're aware of its limitations.

Proprietary to Oracle

PL/SQL is proprietary to Oracle which means if you were to change database vendors then you would have to re-write all your Oracle PL/SQL programs. Also if you use a mixture of databases or develop applications to run on different databases, you will either have to support lots of source code or write your applications in a database-neutral language like Java, VB or C and use the APIs to access the database.

Poor I/O Features

The other limitation of Oracle PL/SQL is that there is very little support for i/o either to read/write files or to read from or write to a user interface. The rationale behind this is that PLSQL is designed for manipulating information from the database and not for processing files or communicating with users. These operations are possible - they just require a little bit more effort!