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# A little history

As mentioned earlier, the DBMS architecture described in this article grew out of the demanding requirements for a system we were contracted to develop. That system is now the Mental Health Clinical Integrated Database (MHCID). It allows clinicians in the mental health sector in Calgary to share clinical data about patients throughout all CRHA-sanctioned mental health clinics and hospitals in the city.

The MHCID system presented us with these difficult requirements:

- Communication between the sites must be supported using modems, so bandwidth was low (less than 30kb/s) and packet latency was high.
- Patient clinical data is very confidential, so must be encrypted when transmitted across the telephone system.
- User access to data must be strictly controlled, to support ethical and organizational requirements.
- The system must log all access to patient data.
- There are hundreds of users - up to 15 simultaneously connected to the server.
- Client workstations were already deployed before we started development (from a previous pilot project). There was only a minimal budget for hardware upgrades.
- The combined budget for software licenses, server equipment and development was relatively small.

Next: Problems with off-the-shelf technology Up: Build your own DBMS!! Previous: Introduction