Uma opção é usar XMLTRANSFORM para renomear um nó. Veja também, por exemplo Renomear nós com XSLT .
with
xmldata as (select xmltype('<root>
<fields>
<a>foo</a>
<b>bar</b>
</fields>
</root>') val from dual),
stylesheet as (select '<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<!-- Identity transformation -->
<xsl:template match="node()|@*">
<xsl:copy>
<xsl:apply-templates select="node()|@*"/>
</xsl:copy>
</xsl:template>
<!-- Identity transformation overridden for element b -->
<xsl:template match="b">
<xsl:element name="c">
<xsl:apply-templates select="node()|@*"/>
</xsl:element>
</xsl:template>
</xsl:stylesheet>' val from dual)
select xmltransform(x.val, s.val) from xmldata x, stylesheet s;
Resultado:
XMLTRANSFORM(X.VAL,S.VAL)
--------------------------------------------------------------------------------
<root>
<fields>
<a>foo</a>
<c>bar</c>
</fields>
</root>
