---
title: Reserve an image id with no accompanying file write
summary: ReserveImageId end-to-end process on SAIF.Services.WCF.Services.ImagingService.
status: draft
owner: SAIF Doc Gen
last_reviewed: 2026-09-22
operation_id: OP-013
trigger: Caller invokes `ReserveImageId` over the `Imaging` route.
---

# OP-013: Reserve an image id with no accompanying file write

ReserveImageId is invoked over the `Imaging` route on `SAIF.Services.WCF.Services.ImagingService`; this page documents the process end to end, from route dispatch to the message the caller receives.

| Field | Value |
| --- | --- |
| **Operation ID** | OP-013 |
| **Trigger** | Caller invokes `ReserveImageId` over the `Imaging` route. |
| **Entry operation** | [`ReserveImageId`](../contracts/imaging-service.md#reserveimageid) |
| **Owning component** | `SAIF.Services.WCF.Services.ImagingService.ReserveImageId` |
| **Inputs** | No request message parts |
| **Outputs** | A freshly reserved, monotonic image id. |
| **Failure behavior** | Generic SOAP fault, per [Faults and error pipeline](../faults.md) |

## Request and response

| Direction | Element | Type | Declared in | Notes |
| --- | --- | --- | --- | --- |
| Request | — | — | — | No input parts — the request message is empty |
| Response | `long` | `long` | BCL (`System`) | A freshly reserved, monotonic image id. |

<!-- Types declared in `SAIF.Services.WCF.Contracts` are attributed to `SAIF.Framework.Core`, inferred from source and package references and marked `*`; their members are not enumerated because the external declaration was not read, marked `**`. -->

## Steps

1. `unitOfWork.GetRepository<Image>().GetNextImageId()` and return, outside any transaction ([BR-WCF-024](../business-rules.md#br-wcf-024-image-id-reserved-before-any-file-write)).
   - On failure: an Oracle/NHibernate exception is logged by the installed error handler and surfaced as a generic SOAP fault with exception detail included.

## Process flow

The following diagram visualizes this process's control flow.

```mermaid
flowchart TD
    A["unitOfWork.GetRepository<Image>().GetNextImageId() and<br>return, outside any transaction ."]
```

## Transaction and side effects

| Aspect | Finding |
| --- | --- |
| Unit of work | `OracleUnitOfWorkFactory` (`IMG`) |
| Commit point | Not applicable — no transaction |
| Records written | `Image` (id reservation only) |
| Downstream calls | None |
| Shared state touched | None |
| Repeat-call behavior | Each call reserves a new, distinct id |

## Logging

| Surface | Written content |
| --- | --- |
| `ErrorLogErrorHandler` → `LogService` | Failure-path exception logging only, carrying method signature, calling user and exception detail; see [Faults and error pipeline](../faults.md) |

## Faults and error handling

| Failure | Fault type the caller receives | Produced by | Source |
| --- | --- | --- | --- |
| Oracle/NHibernate exception | `Generic SOAP fault` | The `ErrorLogErrorHandler` installed by `[LogErrorBehavior]` | src/WCF/SAIF.Services.WCF.Host/Services/ImagingService.cs |

## Authorization

| Requirement | Enforced by | Source | Applies to |
| --- | --- | --- | --- |
| [None in code](../authentication-authorization.md#authorization-enforcement) | IIS authentication on the deployment (see [Activation and hosting](../activation-hosting.md)) | `src/WCF/SAIF.Services.WCF.Host/Services/ImagingService.cs` | This operation |

## Related documentation
- [Index](../index.md)
- [Overview](../overview.md)
- [Architecture](../architecture.md)
- [Activation and hosting](../activation-hosting.md)
- [Operations](../operations.md)
- [Faults and error pipeline](../faults.md)
- [Authentication and authorization](../authentication-authorization.md)
- [Dependencies](../dependencies.md)
- [Configuration](../configuration.md)
- [Operations and processes](../operations-processes.md)
- [Business rules](../business-rules.md)
- [Data model](../data-model.md)
- [Operational runbook](../operational-runbook.md)
- [Tech debt](../tech-debt.md)

> **Note:** Statements marked with `*` were inferred from code structure, naming
> conventions, or contextual evidence where direct confirmation was not available
> in source artifacts. Statements marked with `**` could not be confirmed; treat
> as unknown until verified.

## Sources
- src/WCF/SAIF.Services.WCF.Host/Services/ImagingService.cs