- Customer is migrating a dev environment from SDL Tridion 2011 to SDL Web 8.5.
- When attempting to decommission old publication targets this fails with a timeout error.
- When administrator checks the Content Manager (CM) database PUBLISH_STATES table, records with old publication target are associated with publication IDs for publications which are no longer present.
- Offending publications were removed from CM database when migrating from Tridion 2009 to Tridion 2011 to address database inconsistencies. 
 

- No details available on how the publications were removed; but there should be no concerns as long as they were removed either using the GUI or API.  If publications were removed via stored procedures or database queries, the database may be in an unsupported state.
- Publish transactions removed using Powershell cmdlet Remove-TcmPublishTransactions, completed in 6 hours.
- Legacy publication targets removed after running below Powershell cmdlet, and then manually removing the publication target from CME.

Clear-TcmPublicationTarget -PublicationTargetIds <PUBLICATION_TARGET_ID*>

Timeout on first attempt and the 6 hour time to complete execution may have been due to a buildup of historical publish transactions not having been purged.  Purging unneeded old publishing data, content versions, and other data not needed will help keep database performance optimal.
https://docs.sdl.com/LiveContent/content/en-US/SDL%20Web-v5/GUID-00C1DEE2-8281-4EA8-A8B5-4E9EC3AA3C55

* To verify the publication target ID, open the publication target in a browser, and note the TCM ID.  For example, if the URL for a publication target is as below, then the syntax in Powershell would be
http://localhost/WebUI/item.aspx?tcm=65537#id=tcm:0-4-65537

Clear-TcmPublicationTarget -PublicationTargetIds tcm:0-4-65537