ETL Checklist

ETL Checklist

ETL Checklist is the things to know when you starting a ETL project.

Database Connections: Metadata and the jar files required for Source and Target Databases

Source data : We will have multiple sources and some times Single source also. We need to check is there any redundant data . We need to confirm regarding Data Types and data format. On which basis they are formatting data.

How the customer want to maintain the historical data. Is there any flags for deleted/invalid records. When to use SCD type 2 and SCD type 3 changes.

Logging and Auditing: We need to log all the details to track if any error occurs where it is exactly occurred. Because In our project we will have number of jobs and sub jobs.

So we have to track how many records are successfully inserted/updated

how many records got rejected. Job name, sub job name component name(if any error occurs we can track easily)

Rollback and Restarting Jobs: In ETL process the effected thing is always a Target database. So we need to keep check points in our job so that if any error occurs and results the job to be stopped. In this case ,when restarting the job the job should process from the last saving check point. So that no need to start the entire process again, which save the time and also improves the performance of the project.

Batch Loading: When we have a huge data, it is always better to load the data in multiple chunks rather than loading the entire data at a time. So Batch loading should be implemented.

Dependencies : In Target Database, we need to check for the dependencies like Lookup tables and Parent Tables which are connected with foreign key relationship. Are those having similar data types or not? Need to load the Parent tables first so that the foreign key relation will not get disturbed and also handled easily.

Alerting/Notifications: We have to implement Alerting/Notification mechanism. If any error occurs it should trigger a mail including error description,job name, component name etc.

Documentation: This is also one of the important task . Need to document the mappings in any format. These will be useful like a reference guide.

Thank you



Why build a Data warehouse?

Why build a Data warehouse?

Often when we talk about implementing BI, the first thing we need to look at is how and where is the data? Is it scattered? Is it easy to report on? With this we often need to know if we need to build a reporting database or a data mart or for that matter a data warehouse. We all know WHAT a data warehouse essentially is; here we are going to discuss the WHY.

Consolidate/Integrate Data:

Usually the data in an enterprise is scattered across the various applications and data sources that form the enterprise’s ecosystem. To aid better insights and business decisions, the business users need data from all the various subject areas to be accessible. DWH helps us to consolidate and integrate data from various sources and store in a single data model.


Cleanse data & Enhance data Quality:

DWH includes converting data from different sources into common formats, using common keys, structure, decimal/time formats. We can restructure the data and rename tables and fields so if makes more sense to the users. We can also use master data management to consolidate common data from various sources and build relationships.


Store Historical Data:

DWH is usually used to store huge amounts of historical data that the transactional systems do not /cannot retain. This helps analytics across different time periods, trend analysis.


Speed up Data Retrieval:

In a DWH, the data is structured in such a way that aids faster retrieval. The structure is designed for faster data access, drill down, filtering, and summarization. The transactional systems usually optimized for smaller transactions that inserts/update data in specific tables and access small amount of data. However, BI requires analyzing, aggregating a large amount of data quickly.DWH stores data to help such retrievals.


Unburden transactional Systems:

Executing resource intensive BI queries that access huge amount of data on transactional systems may affect these systems. It may even bring them down affecting business. Building a DWH separate from the transactional systems solves this problem.


Prepare / Pre-aggregate data:

Depending on the business needs, data can be pre-aggregated at various levels and stored in the DWH. This can save time and improve performance of the BI reports. The KPIs that help the business users can also be pre-calculated and stored. Users can then analyse these indicators across dimensions to gain knowledge and insights.


Support Self Service BI:

The DWH either uses dimensional model or easily feeds dimensional models, which can be used to build analytical cubes. These cubes can be used by business users to do Adhoc reporting, slice-n-dice the data and build their own reports.


Increased findability for Business users:

In a DWH, the data is stored in ways that is more meaningful to the business users. Also, the data relations can be easily established. The table names, field names are business user friendly. These make it easier for users to find the data they were looking for.


Helps Data mining / trend analysis / Predictive Analytics:

Once a DWH is created, it makes easier to analyse huge amounts of data and associations to uncover hidden patterns using data mining methodologies. The historical data in DWH can we analysed across time periods to discover trends / perform business predictions.
These are some major reasons / benefits of building a DWH. Though building DWH is a time consuming and complex process, it solves many problems and delivers effective BI.

Shraddha Tambe | Helical IT Solutions