One of the most important factors to determine about the database is its overall size. In the planning, users will need to allocate space for system storage, rollback segments/containers, temporary storage space, log files, and other system files required by the RDBMS, as well as space for Siebel data and indexes. If users allocate too little space for the system, performance will be affected and, in extreme cases, the system itself may be halted. If users allocate too much, they waste space.

The space needed by the database will vary primarily based on the total number and types of users supported. Siebel Systems recommends that users consult the RDBMS technical documentation for more information on these requirements.
The space required for Siebel data and indexes will vary depending on what Siebel functionality users will implement and the amount and nature of data supporting it.

The process for making accurate database size calculations is a complex one involving many variables. The following guidelines will assist users in the process:

Determine the total number, and types, of users of Siebel eBusiness applications (for example, 500 sales representatives and 75 sales managers).

Determine the Siebel functionality that users will implement and the entities required to support them. Typically, the largest entities are as follows:
o Accounts
o Activities
o Contacts
o Forecasts
o Opportunities
o Service Requests

Estimate the average number of entities per user (for example, 100 accounts per sales representative) and calculate an estimated total number of records per entity for the total user base.

Using standard sizing procedures for the specific database, and the Siebel Data Model Reference, calculate the average record size per entity and multiply by the total number of records. Typically, these entities span multiple physical tables, all of which must be included in the row size calculation. This will determine the estimated data sizes for the largest entities.

Users must add additional space for the storage of other Siebel data. A rough guideline for this additional amount would be one-half the storage required for these key entities.

Indexes typically require approximately the same amount of space as data.

Be sure to allow for a margin of error in the total size calculation.

Be sure to factor growth rates into the total size calculation.