You want to backup the native kernel for Java stack before upgrade in case you need to revert it in the future.
Regarding the native kernel, you could refer to note 1912674 for more information.
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restore kernel, retrieve kernel, old kernel, SAPEXEDB,SAR,SAPEXE,kernel release,GetVersionInfo,sapcontrol, backup, back up , KBA , BC-JAS-COR , Enterprise Runtime, Core J2EE Framework , How To
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