I recently worked on a project I which I redesigned sales data warehouse as a STAR schema, using daily file partitions, with a automatic sliding window, and applying data compression at the page level. I ended up reducing a 5 terabyte database to less than 750 GB. I will be writing several articles on the lessons that I learned during the process. Today, I want to talk about how to reseed a identity column if a data load for a dimension fails. Most dimension tables use a surrogate key to…
Tag: DBA
Shrinking the Transaction Log
The transaction log file records all transactions and the database modifications made by each transaction. Heavy application processing against the database can make the transaction log grow quickly. Therefore, the transaction log must be truncated on a ADHOC basis to keep it from filling up. Each physical log file is divided into smaller logical units called virtual log files (VLFs). Truncation provides free space by deleting inactive virtual log files. To avoid running out of log file space or physical disk space if growth is set to unlimited, one should…
Checksum vs Hashbytes
I recently worked on a project I which I redesigned sales data warehouse as a STAR schema, using daily file partitions, with a automatic sliding window, and applying data compression at the page level. I ended up reducing a 5 terabyte database to less than 750 GB. I will be writing several articles on the lessons that I learned during the process. Today, I want to talk about how to generate a hash key by using two built in SQL Server functions. A hash function is any algorithm that maps…
Surrogate Keys
I recently worked on a project I which I redesigned sales data warehouse as a STAR schema, using daily file partitions, with a automatic sliding window, and applying data compression at the page level. I ended up reducing a 5 terabyte database to less than 750 GB. I will be writing several articles on the lessons that I learned during the process. Today, I want to talk about how surrogate keys can be used to tie the dimension tables to the fact tables. I need to start the talk off…