Multi-Version Load in Data Vault
One of the advantages of Data Vault are the easy load patterns that can be used to load hubs, links and satellites. They are well documented in several books about Data Vault. But what happens if you want to load multiple versions in one batch?…
About Data Warehouse Design Patterns and Lazy Programmers
I’m a lazy programmer! That was one important detail I learned from Roelant Vos in his training last week. But there were many other interesting topics. A personal summary of a 3-days class about Data Warehouse Design Patterns. Last week I had the opportunity to attend…
Materialized View Refresh for Dummies
Materialized Views are often used in data warehouses to improve query performance on aggregated data. But what if it takes too long to refresh the materialized views? Here are some basic rules to improve refresh performance. Unlike indexes, materialized views are not automatically updated with…
Issue with the Hint ENABLE_PARALLEL_DML
Performing an ETL with large data sets, it is often a good idea to run DML in parallel. But, in contrast to parallel query or DDL, parallel DML have to be explicitly enabled. You had to issue ALTER SESSION ENABLE PARALLEL DML in the past….
Online Statistics Gathering for ETL – Part 3
Preparing my session on Online Statistics Gathering for ETL for the DOAG conference, I noticed some points that I didn’t covered in the previous two blog posts. The first point is showing the problem that may arise if indexes are involved. The second one is…
10 Tips to Improve ETL Performance – Revised for ADWC
The Autonomous Data Warehouse Cloud (ADWC) is a self-configuring, fast, secure and scalable platform for data warehouses. Does this mean we don’t have to take care anymore about performance of our ETL processes? Which performance tips are still important for us, and where can we…
Gathering Statistics in the Autonomous Data Warehouse Cloud
Optimizer statistics are essential for good execution plans and fast performance of the SQL queries. Of course, this is also the case in the Autonomous Data Warehouse Cloud. But the handling of gathering statistics is slightly different from what we know from other Oracle databases….
Online Statistics Gathering for ETL – Part 2
In the first part we looked at general preconditions for online statistics gathering to work and some restrictions. In this part we’ll take a look at what happens with direct path loads into partitioned tables. Partitioning There are also some points to consider while working…
Online Statistics Gathering for ETL – Part 1
Online Statistics Gathering has been introduced in 12c and is a very handy feature for ETL and batch jobs developers. However the devil is in the detail. There are some points to remember. Let’s take a closer look. Introduction If you are not familiar with…