The correct answer is C. Checking for database prerequisites. According to CompTIA DataSys+ objectives, verifying prerequisites is a critical preparatory step before installing a new database instance. Database prerequisites refer to the minimum and recommended requirements that must be met to ensure a successful installation and stable operation of the database system.

This process typically includes validating disk space availability, CPU capacity, memory (RAM), and network resources, as well as confirming operating system compatibility, required libraries, kernel parameters, and supporting services. DataSys+ emphasizes that failure to meet prerequisites can lead to installation errors, poor performance, instability, or security vulnerabilities after deployment. Therefore, DBAs are expected to thoroughly assess the environment before proceeding with installation.

Option A, performing patch management, refers to applying updates and fixes to existing systems to address bugs or security issues. This occurs after software is installed and operational, not before a new database instance is deployed. Option B, upgrading the database instance, involves moving from one version of a database to another and assumes an existing installation is already in place. Option D, provisioning the configuration, focuses on allocating and configuring resources (such as creating instances, users, or storage structures) after prerequisites have been validated.

CompTIA DataSys+ clearly separates environment validation from deployment and configuration activities. Checking prerequisites is a risk-reduction step that ensures the infrastructure can support the database workload and performance expectations from the start. It also supports capacity planning, compliance, and long-term maintainability.

Therefore, the process of verifying space, hardware, and network resources before installing a database instance is best described as checking for database prerequisites, making option C the correct and fully verified answer.