Oracle 18c

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create table t (col1 xmltype);
insert into t values ('
<MessageData>
  <TextblockParameters>
    <TextblockParameter>
      <tagName>BUSINESSPROCESSID</tagName>
      <value>RETAIL</value>
    </TextblockParameter>
    <TextblockParameter>
      <tagName>SEGMENT</tagName>
      <value>RESIDENTIAL</value>
    </TextblockParameter>
    <TextblockParameter>
      <tagName>TRANSACTIONTYPE</tagName>
      <value>PURCHASE</value>
    </TextblockParameter>
    <TextblockParameter>
      <tagName>LANGUAGE</tagName>
      <value>EST</value>
    </TextblockParameter>
  </TextblockParameters>
</MessageData>');
1 rows affected

select extract(col1, '//value') from t;


EXTRACT(COL1,'//VALUE')


<value>RETAIL</value>
<value>RESIDENTIAL</value>
<value>PURCHASE</value>
<value>EST</value>