There is a Metalink note (563802.1) that has a very good example how XML data storage, partitioning can be achieved in Oracle version 18.104.22.168.0 (the first officially supported XMLDB database functionality) and onwards. Partitioning can be used in such XML situations to spread the I/O load and it also supports, if done correctly, the XMLDB functionality / Oracle database, to use query re-writes during XPath or XQuery statements. See for more information about Query Rewrite support the Oracle XMLDB Developers Guide.
The “new” equi-partitioning functionality, supported from 22.214.171.124.0, but now described in more detail in the 11gR2 XMLDB Developers Manual, also propagates / partitions all underlying structures. As described in the Metalink note:
“In Oracle release 11g the partitioning model is equi-partitioning which means that the underlying storage tables are partitioned too along with the default table partitioning structure. In previous releases only the default table is partitioned, but the underlying storage tables for the types are not.”
So explained in more detail, before 126.96.36.199.0 only the “xdb:defaultTable”, in the following example table “TESTELEMENT”, is partitioned by range. In Oracle 188.8.131.52.0 and onwards also all referred XML structures underneath this entry point are equally partitioned based on this defined range.