The two Silicon Valley companies, which have had joint development and marketing deals since 1998, said they intend to strengthen their relationship.
The overall goal of the reaffirmed partnership, which will last for up to five years, is to make it easier for companies to use Sun and Siebel software in combination.
"Customers don't have to spend time integrating the Sun One software stack with Siebel--we've done it for them," Sun's CEO Scott McNealy said in a statement.
The renewed partnership will result in Siebel's eBusiness Application suite taking better advantage of the reliability and security features in Sun's server software, Sun executives said.
The companies said they will adapt Siebel's applications to take advantage of clustering features in Sun's Solaris operating system and in its identity management and portal software, which are part of theline of Java-based server software.
Sun's portal software should also be able to present information created and delivered by Siebel's own portal tool. Similarly, Sun's identity management software, which authenticates the identity of a person logging onto a network, promises to work with Siebel's applications and with those from other companies.