When sizing a Db2 Big SQL cluster, the two most fundamental resource items are the number of worker nodes and the amount of memory. The number of workers (D) is a primary architectural decision that determines the degree of parallelism (scale-out) for query execution in its Massively Parallel Processing (MPP) engine. The amount of memory (B) allocated to the head and worker nodes is critical for performance (scale-up), directly impacting data caching, sort operations, and the ability to process complex joins efficiently. Together, these two parameters are the main levers for tuning the service's capacity and performance for analytical workloads.

A. Number of physical cores: Sizing for services within a containerized platform like Cloud Pak for Data is based on virtual CPU resources allocated by the scheduler, not direct physical core counts.

C. Number of virtual cores: While virtual cores are a configurable resource, the number of workers and memory are generally the more critical initial sizing factors that define the overall architecture and performance profile.

E. Maximum expected throughput: This is a performance requirement or workload characteristic. It is used to determine the appropriate sizing (workers, memory, CPU), but it is not a resource item you configure directly.

1. IBM Cloud Pak for Data 4.8 Documentation

"Provisioning the Db2 Big SQL service": This official guide details the provisioning process. The user interface and API require the administrator to specify the "Number of Db2 Big SQL workers" and the "Memory per worker (GiB)" and "Memory for the head node (GiB)". This confirms these are direct

mandatory inputs for sizing the instance.

Reference: IBM Cloud Pak for Data 4.8.x Documentation > Services > Db2 Big SQL > Administering > Provisioning the Db2 Big SQL service.

2. IBM Cloud Pak for Data 4.8 Documentation

"System requirements for Db2 Big SQL": The resource requirements section explicitly provides default and recommended values for the number of workers

and the memory and CPU for both head and worker nodes. This highlights that memory and worker count are primary considerations for ensuring a stable and performant deployment.

Reference: IBM Cloud Pak for Data 4.8.x Documentation > Installing and upgrading > System requirements > System requirements for services > System requirements for Db2 Big SQL.