SCD Type 2 is the type of Slowly Changing Dimension that uses a separate table to store both the current and historical data for an attribute. It allows you to maintain a historical record of changes over time while preserving the current value in the main table. This is particularly useful in data warehousing for tracking changes to dimension attributes.

In a star schema, dimension tables are typically denormalized, meaning that hierarchies of attributes are not broken into separate tables. This design is contrary to the snowflake schema, where attributes are often normalized into separate tables to reduce redundancy. In a snowflake schema, the Year, Quarter, and Month attributes might be split into separate tables, leading to more complex joins.

The "in-memory" aspect of a data warehouse means that data is stored in random-access memory (RAM) for faster access and processing. Storing data in RAM allows for high-speed data retrieval and analytics, as data can be accessed more quickly compared to traditional storage on external devices like hard drives. This leads to improved query performance and faster data analysis.

The strategy that involves splitting the data warehouse load process into smaller chunks to ensure availability during business hours is known as "Data Partitioning." Data is divided into partitions, making it more manageable and allowing specific segments to be loaded or accessed without disrupting the entire system. This is a common strategy for balancing data warehouse loads.

Using a snowflake schema, which involves normalizing dimension tables, can lead to increased data redundancy. Normalization breaks down attributes into separate tables, which can result in more complex join operations, increased storage requirements, and potentially slower query performance due to the need for multiple joins.

Columnar databases are frequently preferred in scenarios with heavy aggregation operations. This is because their column-oriented storage allows for efficient processing of aggregation functions, making them well-suited for analytical and data warehousing workloads where aggregations are common.

A staging area in ETL processes is used to temporarily store data before it's transformed and loaded into the data warehouse. It allows for data validation, cleansing, and transformation without impacting the main data warehouse, ensuring data quality before final loading.

Amazon Redshift is a fully managed, performance-tuned data warehousing service provided by AWS. It is designed for analyzing large datasets and offers features like automatic backup, scaling, and optimization to ensure efficient data warehousing in the cloud.

In data warehousing, the process of Extracting, Transforming, and Loading (ETL) data is crucial. ETL involves extracting data from source systems, transforming it to fit the data warehouse schema, and loading it into the data warehouse for analysis. It ensures data quality and consistency.

Data cleansing operations, like removing duplicates and correcting data inconsistencies, are typically performed during the Transformation phase of the ETL process. This is when data is prepared for storage in the data warehouse and is where data quality improvements are made.