Error

The resource ‘0200fe0000624a9370f25b6296a38b4191000d2851466c61736841’ is in use.

logdir is present

Go to Manage -> Settings -> Advanced System Settings. Find ScratchConfig.CurrentScratchLocation and Syslog.global.logDir
If these mention datastores, change that.

vCLS VMs are present

1. Go to the cluster
2. Under Configure >  vSphere Cluster Services, select General
3. click on EDIT VCLS MODE
4. 6. In the Edit vCLS Mode pop up window, click on the second radio option Retreat Mode.

Through CLI

Find the UUID for datastore to be removed.

esxcli storage filesystem list

Unmount

esxcli storage filesystem unmount [-u _UUID_ | -l _label_ | -p _path_ ]

Note: If the VMFS filesystem you are attempting to unmount has active I/O or has not fulfilled the prerequisites to unmount the VMFS datastore, you see an error in the VMkernel logs similar to:

WARNING: VC: 637: unmounting opened volume (‘4e414917-a8d75514-6bae-0019b9f1ecf4’ ‘LUN01’) is not allowed.
VC: 802: Unmount VMFS volume f530 28 2 4e414917a8d7551419006bae f4ecf19b 4 1 0 0 0 0 0 : Busy

verify that the datastore is unmounted, run this command:

esxcli storage filesystem list

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references:

1. How to detach a LUN device from ESXi hosts (2004605) (vmware.com)
2. Steps to fix unable to unmount/delete VMFS Datastore: the resource is in use (bobcares.com)
3. How to Disable vCLS on a Cluster via Retreat Mode (91890) (vmware.com)