Update durable-functions-orchestrations.md

Reducing the recommended instance ID length from 256 to 100 since 100 is the maximum allowed by the MSSQL storage provider.

Author: cgillum

articles/azure-functions/durable/durable-functions-orchestrations.md

@@ -27,13 +27,15 @@ Each *instance* of an orchestration has an instance identifier (also known as an
 
 The following are some rules about instance IDs:
 
-* Instance IDs must be between 1 and 256 characters.
+* Instance IDs must be between 1 and 100 characters.
 * Instance IDs must not start with `@`.
 * Instance IDs must not contain `/`, `\`, `#`, or `?` characters.
 * Instance IDs must not contain control characters.
 
 > [!NOTE]
 > It is generally recommended to use autogenerated instance IDs whenever possible. User-generated instance IDs are intended for scenarios where there is a one-to-one mapping between an orchestration instance and some external application-specific entity, like a purchase order or a document.
+> 
+> Also, the actual enforcement of character restriction rules may vary depending on the [storage provider](durable-functions-storage-providers.md) being used by the app. To ensure correct behavior and compatibility, it's strongly recommended that you follow the instance ID rules listed previously.
 
 An orchestration's instance ID is a required parameter for most [instance management operations](durable-functions-instance-management.md). They are also important for diagnostics, such as [searching through orchestration tracking data](durable-functions-diagnostics.md#application-insights) in Application Insights for troubleshooting or analytics purposes. For this reason, it is recommended to save generated instance IDs to some external location (for example, a database or in application logs) where they can be easily referenced later.