Chapter 10 - Teradata Writes and Blocks
“Either write something worth reading or do something worth writing.”
- Benjamin Franklin
A Teradata Write
- For SQL writes, Teradata uses Write Ahead Logic (WAL) to manage disk write operations.
- Read the Data Block (if not in memory use Master Index > Cylinder Index > Data Block).
- Place before-image of row into the Transient Journal buffer and write to the WAL log on disk.
- Data blocks are always updated in Memory, but not always written to disk immediately.
- The row's after-image (REDO row) is written to the WAL log on disk.
- WAL will often batch up modifications from multiple transactions and write with a single I/O.
- All updated data blocks in memory will be eventually aged out and written to disk. ...