The outcome of your environment assessment can impact the migration strategy you choose. Therefore, ensure your migration team has a detailed understanding of the current setup very early in the process. Doing this also helps in identifying possible challenges at an early stage.
As a reference in later stages or for any troubleshooting purpose, it useful to document the objects you do not need to migrate since you will no longer use them in Exasol.
The following section lists all the things you should consider documenting.
Document all the data objects you want to migrate. For instance:
- Which Databases must be migrated? A database in Teradata will map to a schema in Exasol.
- Check for potential data types for which you cannot do a 1:1 mapping with Exasol, for example, BLOB types
- Run the query in Appendix A: Data Type Mapping to get an overview of all the data types used and the possible challenges
- Size of the table
- Check if you have Non-Standard SQL elements which are supported only by Teradata
- To get an overview of all views, run the query in Appendix B: Extract View Texts from Teradata
- User-Defined Functions can be either translated to Exasol’s PL / SQL style functions or rewritten using Exasol’s UDF framework
- To get an overview of all functions, run the query in Appendix C: Overview of Teradata Functions
- Stored Procedures
- Stored Procedures can be converted into Exasol LUA Scripts
- To get an overview of all stored procedures, run the query in Appendix D: Overview of Teradata Stored Procedures
- Macros can be converted to Exasol LUA scripts
- Triggers are not supported in Exasol
- You don’t need to migrate any indices as Exasol creates indices automatically on the fly
Document all the ETL Processes in your Teradata warehouse, such as:
- Data Integration / ETL Tools / Scheduling Tools
- Handwritten procedures for ETL / ELT processing
- Data Sources
- For each data source document
- Security (e.g, needed users)
- Loading frequency / loading window
- Network bandwidth
- Loading SLAs
BI Tools and Other Applications
Document all applications used by your current Teradata data warehouse, such as:
- BI tools
- SQL Editors
- Data Science Applications (e.g., integration to R and Python)
- Other applications which access data from the DWH
Check the connectivity for all of your existing tools to Exasol (see Ecosystem Overview). If any tool is not supported, look for alternatives tools. For example, you can use DBVisualizer or DBeaver as an alternative to Teradata Studio.
Document all the security requirements currently implemented in Teradata that must be migrated to Exasol, such as:
- Encryption of data at rest and in motion
- The users / roles and their privileges (run query in Appendix E: Overview of Users and Roles to get an overview)
- Are users authenticated via LDAP or Active Directory?
- Do you have Row or Column Level Security implemented?
- Auditing capabilities
Document all your existing environments and consider them for your migration plan. For example:
- Production environment
- Pre-Production / QA environment
- Development environment
For your general migration planning, consider the following operational aspects and include them in your migration plan to Exasol:
- General SLA requirements
- Document the current backup strategy
- Document the current disaster recovery strategy
- Document your enterprise monitoring tools