Database data block sizes and alignments are variable. This permits a designer the flexibility of designing tables without having to spend time balancing data types, row sizes, and block sizes to optimize their storage.
Critical Sizing Variables
The critical variables for sizing database tables and indexes are the following:
- Row size
- Estimated cardinality
- Presence of fallback
Table headers are a fixed variable, but must be considered when projecting the sizes of your tables. Take multivalue compression into account when sizing table headers (see Compression Types Supported by Vantage).
LOB and XML Sizing Variables
Each chunk of a BLOB, CLOB, or XML string stores an 8-byte length followed by as much as a 64 KB data fragment. LOBs are stored outside its base table row in a subtable. See Sizing a LOB or XML Subtable for more information.