I see the statement below in the Upgrade document [Applications Upgrade Guide (from HP SErvice Manager 9.3x without Process Designer Content Pack installed) pdf]
Make sure that you have upgraded your server and the client to the latest version before you attempt to run an application upgrade. This allows the upgrade utility to call the new functions in the latest server and client and to take full advantage of all of the application features following an upgrade.
Is this referring to updating Production Server(RTE) and client before we take the database backup for building Dev and Test setups?
We have not done it and completed building SM9.40 custom upgrade and now we are facing issue while appying the custom upgarde in Test Environment.
Would like to understand if this upgrading RTE and Clinet in PROD is mandatory (at the startof the activity)or can be skipped now and done before applying the custom upgrade in Production?