In Azure environment, administrator may notice that some of the elastic application layers fail to get attached in the Layered VDIs.

Event logs on the VDI may show the following error:

Source: Citrix Layering Service
Event ID: 1310
Message: Encountered error attaching the disk for layer <layername> version <versionInfo>.Layer version will not be attached.

Ulayersvc.log on the VDI might show the following pattern:

INFO 5 LayerAttachService: Attaching <NameOfTheLayer> with 3 tries
INFO 5 VirtualDiskService: Attaching virtual disk <AzureVHDFilePath>
ERROR 4 NativeMethodLogger: Failed to open virtual disk <AzureVHDFilePath> with access 'Read': Error code 1816
ERROR 4 ComponentActivatorExceptionInterceptor: Method 'Open' returned error Not enough quota is available to process this command.

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The default handle quota for the Azure File share where the Elastic layers are stored is insufficient for the user load.

Increasing the Azure share handle Quota limit should fix the issue. 

Reference: https://learn.microsoft.com/en-us/azure/storage/files/smb-performance?tabs=portal#register-for-increased-file-handle-limits-preview