A business currently has a labor-intensive process to manually upload orders from an external OMS.

The current bottleneck is caused by the need to resolve Salesforce Internal IDs ($001...$) for the Account lookup before orders can be imported. This can be completely bypassed by using External IDs (Option D) and the Upsert operation (Option C).

External IDs: By marking a unique field from the OMS (like OMS_Account_Number__c) as an External ID in Salesforce, the developer creates a "foreign key" that Salesforce understands.

Upsert Wizard: When using the Data Loader's Upsert wizard, the user is asked which field should be used to match the parent Account. By selecting the OMS_Account_Number__c external ID, the Data Loader allows the user to map the orders directly to accounts using the OMS number found in the CSV file.

Salesforce will automatically find the correct Account ID in the background. This eliminates the "export-and-VLOOKUP" step entirely. Option A (Insert) would still require internal IDs. Option B (sorting) helps with performance in massive loads but doesn't solve the manual ID matching problem. Using Upsert with External IDs is the platform-recommended way to streamline recurring data integrations.