Building off of this amazing post on how to configure multi site, I was working on retiring a site in VCD 10.2.x and discovered there is no option to disconnect a site in the UI until 10.3.x. When retiring an instance for any reason and needing to disconnect the instance from a Multi Site configuration this is a process:

Authenticate to the VCD API following this KB(I always forget these steps using postman…), this should be done at the provider level and with a SYSADMIN level account: https://kb.vmware.com/s/article/56948
Once you have the bearer token from the above step, run the following command to see what site(s) the VCD instance is linked to by running this command. Changing the host name to match the instance in question
Make sure to add the following header as well
Content-Type application/vnd.vmware.admin.siteAssociation+xml
GET https://bblab-vcd02.com/api/site/associations/
Capture the body that is returned which will list out the instance(s) this sit is connected to and their current state. The return body may be large but it is required for the next steps Expand source
Locate the line that states “remove” and add the SITE_UUID to the end of your URL similar to my example<Link rel=”remove” href=”https://bblab-vcd01.com/api/site/associations/c913fce4-e24b-4c38-83aa-3f66c8ae8ae7” type=”application/vnd.vmware.admin.siteAssociation+xml”/>Update postman URL to: https://bblab-vcd02.com/api/site/associations/c913fce4-e24b-4c38-83aa-3f66c8ae8ae7
Within the return body above, capture from <SiteAssociationMember to —–END PUBLIC KEY—–</PublicKey> and paste that into the body as RAW XML as shown below for removing bblab-vcd01 from bblab-vcd02.
Now run that as a DELETE and the return should look similar to the following
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><Task xmlns="http://www.vmware.com/vcloud/v1.5" xmlns:ovf="http://schemas.dmtf.org/ovf/envelope/1" xmlns:vssd="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/CIM_VirtualSystemSettingData" xmlns:common="http://schemas.dmtf.org/wbem/wscim/1/common" xmlns:rasd="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/CIM_ResourceAllocationSettingData" xmlns:vmw="http://www.vmware.com/schema/ovf" xmlns:ovfenv="http://schemas.dmtf.org/ovf/environment/1" xmlns:vmext="http://www.vmware.com/vcloud/extension/v1.5" xmlns:ns9="http://www.vmware.com/vcloud/versions" cancelRequested="false" expiryTime="2021-12-23T01:14:57.381Z" operation="Updating Site bblab-vcd02.com(c913fce4-e24b-4c38-83aa-3f66c8ae8ae7)" operationName="siteUpdate" serviceNamespace="com.vmware.vcloud" startTime="2021-12-09T01:14:57.381Z" status="queued" name="task" id="urn:vcloud:task:8d84c54f-d121-4332-8de0-5700a63696cf" href="https://bblab-vcd02.com/api/task/8d84c54f-d121-4332-8de0-5700a63696cf" type="application/vnd.vmware.vcloud.task+xml"> <Link rel="edit" href="https://bblab-vcd02.com/api/task/8d84c54f-d121-4332-8de0-5700a63696cf" name="task" type="application/vnd.vmware.vcloud.task+xml"/> <Link rel="edit" href="https://bblab-vcd02.com/api/task/8d84c54f-d121-4332-8de0-5700a63696cf" name="task" type="application/vnd.vmware.vcloud.task+json"/> <Owner href="https://bblab-vcd02.com/api/site/c913fce4-e24b-4c38-83aa-3f66c8ae8ae7" id="urn:vcloud:site:c913fce4-e24b-4c38-83aa-3f66c8ae8ae7" name="bblab-vcd02.com" type="application/vnd.vmware.vcloud.site+xml"/> <User href="https://bblab-vcd02.com/api/admin/user/4ac4c656-a5f4-48e7-b5cd-fc29847f2e2e" id="urn:vcloud:user:4ac4c656-a5f4-48e7-b5cd-fc29847f2e2e" name="adm.bbazan" type="application/vnd.vmware.admin.user+xml"/> <Organization href="https://bblab-vcd02.com/api/org/a93c9db9-7471-3192-8d09-a8f7eeda85f9" id="urn:vcloud:org:a93c9db9-7471-3192-8d09-a8f7eeda85f9" name="System" type="application/vnd.vmware.vcloud.org+xml"/> <Details></Details> <VcTaskList/></Task>
Running the above “GET” command to return the associated sites will no longer return the removed site https://bblab-vcd02.com/api/site/associations/
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><SiteAssociations xmlns="http://www.vmware.com/vcloud/v1.5" xmlns:ovf="http://schemas.dmtf.org/ovf/envelope/1" xmlns:vssd="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/CIM_VirtualSystemSettingData" xmlns:common="http://schemas.dmtf.org/wbem/wscim/1/common" xmlns:rasd="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/CIM_ResourceAllocationSettingData" xmlns:vmw="http://www.vmware.com/schema/ovf" xmlns:ovfenv="http://schemas.dmtf.org/ovf/environment/1" xmlns:vmext="http://www.vmware.com/vcloud/extension/v1.5" xmlns:ns9="http://www.vmware.com/vcloud/versions" href="https://bblab-vcd02.com/api/site/associations" type="application/vnd.vmware.admin.siteAssociations+xml"> <Link rel="edit" href="https://bblab-vcd02.com/api/site/associations" type="application/vnd.vmware.admin.siteAssociations+xml"/> <Link rel="edit" href="https://bblab-vcd02.com/api/site/associations" type="application/vnd.vmware.admin.siteAssociations+json"/> <Link rel="add" href="https://bblab-vcd02.com/api/site/associations" type="application/vnd.vmware.admin.siteAssociation+xml"/> <Link rel="add" href="https://bblab-vcd02.com/api/site/associations" type="application/vnd.vmware.admin.siteAssociation+json"/> <Link rel="down" href="https://bblab-vcd02.com/api/site/associations/localAssociationData" type="application/vnd.vmware.admin.siteAssociation+xml"/> <Link rel="down" href="https://bblab-vcd02.com/api/site/associations/localAssociationData" type="application/vnd.vmware.admin.siteAssociation+json"/> <Link rel="up" href="https://bblab-vcd02.com/api/site" type="application/vnd.vmware.vcloud.site+xml"/> <Link rel="up" href="https://bblab-vcd02.com/api/site" type="application/vnd.vmware.vcloud.site+json"/></SiteAssociations>
On the target site side(in this example bblab-vcd01 or bblab-vcd02) we see the connection is now listed as “ASYMMETRIC”
<RestEndpoint>https://bblab-vcd02.com</RestEndpoint> <BaseUiEndpoint>https://bblab-vcd02.com</BaseUiEndpoint> <SiteId>urn:vcloud:site:c913fce4-e24b-4c38-83aa-3f66c8ae8ae7</SiteId> <SiteName>bblab-vcd02.com</SiteName> <PublicKey>-----BEGIN PUBLIC KEY-----MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3cOHHCKWMJEx6Kgvta+cPWowhP1T3jpnFHOzyNUDJFH8JQ4s6+KrJq25isrhd1btevG4iuvZG8pQEIFq2HMM/rYftxw9X/vWUNE0onuRVA7T2R-----END PUBLIC KEY-----</PublicKey> <Status>ASYMMETRIC</Status>

Make sure to remove the other side as well, in versions before 10.3 not removing both sides of the connection may cause performance issues
For more multisite goodness: https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/vcat/architecting-multi-site-vmware-vcloud-director.pdf