Improve Deep Data Security lab scenarios

docs/troubleshooting.md

@@ -14,6 +14,51 @@ Check:
 
 Remove or adjust `adb_db_version` in `terraform.tfvars`. Database version availability depends on region, tenancy, and service limits. For a real Oracle Deep Data Security lab, use a version compatible with Oracle AI Database 26ai.
 
+## Autonomous Database Name Already Exists
+
+Autonomous Database `db_name` must be unique in the tenancy and region. If apply fails with a message such as `a database named DDSLAB already exists`, change the value in `terraform.tfvars`:
+
+```hcl
+adb_db_name = "DDSLAB2"
+```
+
+Then create a new plan. Do not reuse the old `tfplan`:
+
+```bash
+rm -f tfplan
+terraform plan -out tfplan
+terraform apply tfplan
+```
+
+If you intended to use an existing Autonomous Database instead of creating a new one, do not apply the Terraform ADB resource. Run the SQL scenario scripts directly against the existing database connection string.
+
+## Bastion Image Is Not Compatible With Shape
+
+When `enable_compute_bastion = true`, the image OCID must be compatible with `bastion_shape` in the selected region. If apply fails with `Shape ... is not valid for image ...`, either:
+
+- set `enable_compute_bastion = false` and use OCI Bastion Service; or
+- select a compatible platform image for the configured shape and region.
+
+Example OCI CLI lookup for an Oracle Linux image compatible with `VM.Standard.E5.Flex`:
+
+```bash
+oci compute image list \
+  --region eu-madrid-1 \
+  --compartment-id <compartment_ocid> \
+  --operating-system "Oracle Linux" \
+  --shape VM.Standard.E5.Flex \
+  --sort-by TIMECREATED \
+  --sort-order DESC \
+  --query 'data[0].id' \
+  --raw-output
+```
+
+Use the returned OCID in `terraform.tfvars`:
+
+```hcl
+bastion_image_ocid = "ocid1.image.oc1.eu-madrid-1..."
+```
+
 ## Database Is Not Reachable
 
 Check:
@@ -35,4 +80,3 @@ Check:
 ## Reset Does Not Remove Everything
 
 Run the scenario `sql/99_reset.sql` and manually validate remaining objects. In shared environments, confirm before dropping schemas.
-