Abstract: With the development of society and the rapid change of technical framework,it has become a trend for the daily system to replace the old system with the new one.The replacement of the old system with the new system will inevitably involve the data docking between the old system and the new system.In the system construction of an organization in a city,the project needs to migrate all business data of the old system to the new system.Due to the inconsistency of table space,table structure and table field between the old and new systems,in order to ensure the consistency and integrity of data,ensure that data before and after migration is not missing,and ensure that dirty data does not migrate to affect the operation of the new system,how to migrate data between the old and new systems has become a top priority in the project.In order to solve the problem of data migration,this paper designs a data migration process based on ETL tools,and obtains a complete data migration process line through combination and series connection,thus realizing data migration to complete data docking between old and new systems.This paper elaborates the following problems and solutions for data migration:1)Common errors and solutions in data flow.2)Data migration problems and solutions with inconsistent data types.3)Inconsistent length of field in target database of data migration and solutions.4)How to re-change the original data when data migration is completed Problems and solutions of adjusting migration measurement.Based on this,this paper makes a brief analysis and summary of the problems in the process of data migration and the countermeasures to solve these problems.

Key words: Data migration, Data transfer, ETL tools, SQL statement