Amazon.com Inc. and Salesforce.com Inc., two of Oracle Corp.’s biggest customers, are actively working to replace Oracle software running on crucial business systems with lower cost open-source database software, the Information reported, citing people familiar with the discussions.

The technology news site said Amazon and Salesforce have already made significant progress toward weaning themselves off Oracle all together. They have ample motivation to do so: While Oracle’s database is widely considered the world’s most advanced, it’s also expensive compared with the competition, the Information reported. Oracles shares slid in New York Tuesday.

Amazon began exploring Oracle alternatives in the early 2000s, and is further along, according to the report. It has already switched over two internal databases that underpin its massive e-commerce operation to open-source NoSQL from Oracle, the Information said, citing two people with knowledge of the change.

Salesforce, which uses Oracle’s database in its customer management and marketing automation software, has also been developing a database replacement, code-named Sayonara -- Japanese for “goodbye” -- and is now ready to deploy it internally, the Information reported, citing a former Salesforce employee with knowledge of the matter. Salesforce expects to be completely weaned of Oracle by 2023, the person said, according to the publication.

Oracle, Salesforce and Amazon declined to comment to the Information.

Redwood City, California-based Oracle had almost $38 billion in revenue in the fiscal year ended in May. The company co-founded by Larry Ellison sells a variety of business software applications and hardware products, but its database software -- used by most of the Fortune 500 companies -- is its flagship product.

Oracle shares were down 1.4 percent to $46.62 at 11:24 a.m. in New York. They are up 21 percent in the past 12 months.