Plan: "1 to change" but seems to want to destroy

Terraform
1

We are resizing an Azure Netapp files pool/volume and the plan mentions changing the resource for the resize. The plan actually throws an error because of our prevent destroy true flag on the volume. Is the prevent destroy not compatible with this?

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform planned the following actions, but then encountered a problem:

  # module.netappfilespool01.azurerm_netapp_pool.anf will be updated in-place
  ~ resource "azurerm_netapp_pool" "anf" {
        id                  = ""
        name                = ""
      ~ size_in_tb          = 8 -> 16
        tags                = {
            "budget_code"       = "570"
            "deployment_method" = "terraform"
            "pipeline"          = ""
            "w4-source"         = ""
            "wiki"              = ""
        }
        # (5 unchanged attributes hidden)
    }
Plan: 0 to add, 1 to change, 0 to destroy.
╷
│ Error: Instance cannot be destroyed
│ 
│   on ../../modules/netappfiles/netappfilesvolume/netappfilesvolume.tf line 6:
│    6: resource "azurerm_netapp_volume" "anf" {
│ 
│ Resource module.netappfilesvolume01.azurerm_netapp_volume.anf has
│ lifecycle.prevent_destroy set, but the plan calls for this resource to be
│ destroyed. To avoid this error and continue with the plan, either disable
│ lifecycle.prevent_destroy or reduce the scope of the plan using the -target
│ flag.
╵
##[error]Terraform command 'plan' failed with exit code '1'.
2

You’ve clipped some relevant lines off the top of your Terraform output. It would have said:

Terraform planned the following actions, but then encountered a problem:

which explains that it produced a partial plan, and then found a resource which would need to be destroyed to apply the change.

If you remove the prevent_destroy and run a plan - only a plan! - then Terraform will reveal what change makes it believe the volume must be destroyed and replaced, via forces replacement comments in the plan.