Dimensioning Rules

The Fixed Block size for Real Objects can be configured with dbamboot to1 KB (default), 4 KB, 16 KB or 64 KB

The value to take here depends on how much memory is needed for 80 or 90% of the entries. An entry with about 10 standard attributes like password, telephone number, postal address will fit into 1 KB block. If many entries have space consuming attributes like certificates or photos, a bigger value should be taken. Note that for the entries that do not fit in one block, the system will have to create overflow blocks, which have consequences on the performance.

Choose the one, which allows to confine and to contain the information of an entire entry for at least 80 % of all entries.

This will so lead to the ideal situation of having to handle overflow records only for 20 % of all entries.

If N is the number of entries and K the configured block size in KB, the size of the REAL logical device will be

[KB] or [GB]

where

N = number of objects/ entries in the directory

K = said basic size of the Real Object in KB.

The following values can be deduced from the size of the Real Objects (REAL) logical device, i.e.:

Therefore, the size of this logical device will be:

Setting:

I = Number of indexed attributes
D = Density of indexes attribute values
Cl = cluster size in MB

The size of the AVIDX logical device will be in GB

This rule implicitly takes in account that all possible indexes, including CONTAINS (i.e.: INITIAL, FINAL, CONTAINS, ANY (presence) and APPROXIMATE (phonetic match)) will be created for all indexed attributes.

A minimum size of 256 MB is required. For best performance consider:

TRANSLog = 2 times DBAM cache size and 4 GB behind.