After upgrading Cloud Pak for Data, the state of the Db2 Big SQL custom resource is NotReady

After Cloud Pak for Data is upgraded to 4.8.8 but before the Db2® Big SQL service instance is upgraded, the state of the Db2 Big SQL custom resource is NotReady.

Symptoms

Run the following command:
oc get bigsql
Example output:
NAME                      DB2UCLUSTER               STATE      AGE
bigsql-1737059146205611   bigsql-1737059146205611   NotReady   5h37m
The logs for the db2u-operator-manager pod shows entries with a reference to Credential followed by context deadline exceeded. For example:
1.7371398140628374e+09	INFO	controllers.BigSQL	Credential	{"namespace": "liteproject", "name": "bigsql-1737059146205611"}
1.7371398740872245e+09	ERROR	controller.bigsql	Reconciler error	{"reconciler group": "db2u.databases.ibm.com", "reconciler kind": "BigSQL", "name": "bigsql-1737059146205611", "namespace": "liteproject", "error": "rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem
	/root/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:266
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2
	/root/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:227

Resolving the problem

Do the following steps;

  1. Restart the Db2U API component in the Db2 Big SQL head and worker pods:
    oc exec c-bigsql-${bigsql_instance_id}-db2u-0 -- sv restart db2uapi
oc exec c-bigsql-${bigsql_instance_id}-db2u-1 -- sv restart db2uapi
  2. Repeat step 1 for any other c-${bigsql_instance_id}-db2u-n pods.
  3. Check that the Db2 Big SQL custom resource has moved back to the Ready state:
    oc get bigsql bigsql-${bigsql_instance_id}