What Load Type should I choose when I am loading data from source to bronze layer ?

When determining the appropriate load type (full, initial/incremental, or CDC) for your SQL database tables into a Bronze layer, you need to consider several key criteria. Here's a breakdown:

1. Data Volume and Table Size:

• Full Load:
  • Suitable for small to medium-sized tables where a complete refresh is feasible within acceptable timeframes.
  • Also appropriate for tables where historical changes are not critical.
• Initial/Incremental Load:
  • Essential for large tables to avoid overwhelming system resources with frequent full loads.
  • Necessary when only changes need to be reflected in the Bronze layer.
• CDC (Change Data Capture):
  • Best for tables with high transaction volumes and a need for near real-time data updates.
  • Required when capturing every change (inserts, updates, deletes) is crucial.

2. Change Frequency and Volatility:

• Full Load:
  • Acceptable for tables with infrequent changes or where changes are made in large batches.
• Initial/Incremental Load:
  • Necessary for tables with moderate to frequent updates.
• CDC:
  • Mandatory for tables with very frequent changes and a demand for low-latency data replication.

3. Availability of Change Tracking Mechanisms:

• Full Load:
  • No specific requirement.
• Initial/Incremental Load:
  • Requires a reliable method to identify changes, such as:
    • Timestamps (e.g., "modified_date," "created_date" columns).
    • Version numbers.
    • Status flags.
• CDC:
  • Relies on database-level CDC features or transaction logs.

4. Data Dependency and Relationships:

• Consider the dependencies between tables. If a table is a parent table, and many child tables depend on it, then changes in the parent table may require changes in the child tables.
• This can impact the complexity of incremental loads and CDC.

5. Performance Requirements:

• Full Load:
  • Can put a significant strain on source and target systems.
• Initial/Incremental Load:
  • More efficient than full loads, but requires careful optimization.
• CDC:
  • Can add overhead to the source database, so it's important to assess the impact.

6. Data Retention and History:

• Full Load:
  • Replaces the entire table, so historical data is lost unless explicitly archived.
• Initial/Incremental Load:
  • Preserves historical data, but may require additional logic to track changes.
• CDC:
  • Provides a detailed history of all changes.

7. Business Requirements:

• Consider the business needs for data freshness and accuracy.
• Real-time reporting may necessitate CDC, while less time-sensitive reporting may be satisfied with incremental or full loads.

Practical Approach:

• Categorize Tables: Group tables based on their characteristics (size, change frequency, importance).
• Prioritize: Focus on the most critical tables first.
• Evaluate Change Tracking: Determine if suitable change tracking mechanisms exist.
• Proof of Concept: Test different load types on a subset of tables.
• Document: Create a detailed plan outlining the load type for each table and the rationale behind it.

By carefully evaluating these criteria, you can develop a robust and efficient data loading strategy for your Bronze layer.