Hach WIMS Multiuser supports Oracle or MS SQL server database management systems with the DB Support option.  See Software Requirements for supported versions. Hardware requirements for the database server are set by the database management system's requirements.  Hardware recommendations are dependent on operating system, number of users, amount of data being tracked, other applications using the same database server, etc and are difficult to quantify.  However, the general rule is the more RAM, number of CPUs, CPU speed, and disk space the better as budgets allow.

While the above specifications were written for physical hardware, they also apply to virtualization (see Microsoft links for platform specific information).

The following links are provided from Microsoft for your information:

Hardware and Software Requirements for Installing SQL Server 2012 NOTE: For WIMS-MU users (i.e. without DB Support) WIMS installs SQL 2012 Express Edition.  Windows 10 is supported with SQL 2012 Express Edition although it is not listed in the linked Microsoft article. 

NOTE:  As of Sept 17th, 2020, WIMS installs SQL 2012 Express (unless DB Support is added to license).  As SQL 2012 support ends in 2021, users may want to manually install SQL 2019 Express. This will NOT violate your WIMS license agreement.  SQL 2019 requires Windows 10 or Server 2016 or later (please see https://docs.microsoft.com/en-us/sql/sql-server/install/hardware-and-software-requirements-for-installing-sql-server-ver15 for more info). You can also perform an in-place upgrade to 2019 post install - See SQL 2012 to SQL 2019 for instructions.

Hardware and Software Requirements for Installing SQL Server 2014 - (NOTE: Supported operating systems: Windows 7, Windows Server 2008 R2, Windows Server 2008 Service Pack 2, Windows Vista Service Pack 2, DOES NOT SUPPORT WINDOWS XP)

The following links are provided from Oracle for your information:

Oracle9i Database Installation Guide Release 2 (9.2.0.2.1) for 64-Bit Windows

Oracle9i Database Installation Guide Release 2 (9.2.0.1.0) for Windows

See Also: 

How fast does the WIMS (OPS SQL) database grow based on the number of points I track?

Hach WIMS Architecture

Hardware Requirements for Hach WIMS Client 7.x.x

Bandwidth Requirements