This section provides the formula for estimating VCI disk space requirements.

Disk space = (number of rows in tables) x (number of bytes per row) x (compression ratio) + (WOS size)

Number of bytes per row

Number of bytes per row = (19 + (number of columns specified in CREATE INDEX) / 8
                                    + (number of bytes per single column value)) x 1.1

Note: Round up the result to the nearest integer.

Compression ratio

Specify a value between 0 and 1. Since compression ratio depends on the data being compressed, use actual data or test data that simulates it, then compare the value with the estimation result. As a guide, the compression ratio measured with the Fujitsu sample data is shown below:

• Data with high degree of randomness (difficult to compress): Up to approximately 0.9 times.

• Data with high degree of similarity (easy to compress): Up to approximately 0.5 times.

WOS size

WOS size = (number of WOS rows) / 185 x 8096

One row is added to the number of WOS rows for each INSERT and DELETE, and two rows are added for UPDATE. On the other hand, the number decreases to 520,000 rows or less during conversion to ROS performed by the ROS control daemon.