Data validation is the process of comparing data from both the source and thedestination database tables to ensure they match.

TheData Validation Tool (DVT)is an open source tool that can connect to data stores and perform checksbetween your source database and Spanner. We recommend using it to performbasic validations as a part of your migration, such as the following:

• Check that all tables were created and that all schema mappings arecorrect.
• Match the total number of rows for each table.
• Extract random rows to verify consistency.
• Validate your columns, for example, usecount,sum,avg,min,max, orgroup by.
• Compare any cyclic redundancy checks or hash functions at the row level.

To perform more specific validations, build custom checks during migration.