The Gimmal-Link (Legacy) app is installed in the Office365 tenant to enable secure access to the SharePoint environment from Gimmal Link (Legacy). It uses an OAuth token passing flow to authenticate to SharePoint in the app context. Gimmal Link (Legacy) uses the clientID and client secret of the app to securely authenticate through Azure Access Control Services.
You must install the Gimmal Link SharePoint app under the following conditions:
You are creating a CSOM Claims-Based Authentication setup with SharePoint Online/ O365, or
You are creating a CSOM Certificate-Based Authentication setup with SharePoint on-premises
No other configurations require that you install the SharePoint app.
Review https://msdn.microsoft.com/en-us/library/office/fp142384.aspx to understand more about SharePoint Add-On security model.
If you are using CSOM Claims-Based authentication mode to connect to SharePoint Online/O365 or using CSOM Certificate-Based Authentication to connect to SharePoint on-premises, then the Gimmal Link App Add-On must be installed to access SharePoint contents by performing the following steps:
Download the ERP-Link App 1.0 from the Gimmal software download site.
Download version 5.1 of the Gimmal App Installer and the associated documentation from the Gimmal software download site.
You must use v5.1 of the Gimmal App Installer. Earlier versions are not compatible.
Follow the steps in the documentation to add the app to the SharePoint App Catalog in the target environment.
Install the app on any site collection that you want to use with Gimmal Link for archival and retrieval processes.