We were using SUSE Linux Enterprise Server for SAP Applications subscription and it was expired one month back.
Now our all VMs are running on SUSE Linux Enterprise 15 SP0 OS version and we want to upgrade it to SLES 15 SP6.
Please let us know whether we can upgrade the OS version without affecting the current subscription!
If your subscription expired a month ago then you don’t have a current subscription. That will affect your ability to upgrade as you won’t have access to updated packages.
Whilst SLES for SAP Applications includes Extended Service Pack Overlay Support (ESPOS) this has expired for SLES for SAP Applications 15 GA (SP0), SP1, and SP2 - see https://www.suse.com/lifecycle/#suse-linux-enterprise-server-for-sap-applications-15
The upgrade path for you from SLES for SAP Applications 15 GA to SP6 is therefore SLES for SAP Applications 15 (SP0) to SP1 to SP2 to SP3 (the earliest supported*) to SP6 (the latest supported*) - you are allowed to skip up to two supported* service packs.
However part of the supported* upgrade procedure is to install all available outstanding patches which you won’t have access to - the best you can do is to download and use the DVD1 media for each of the upgrade target versions.
*though since you don’t currently have a subscription you also don’t have support