The ROMIO Users Guide is in the file users-guide.ps.gz.

The book ``Using MPI-2: Advanced Features of the Message-Passing
Interface,'' by William Gropp, Ewing Lusk, and Rajeev Thakur, 
MIT Press, 1999, provides a tutorial introduction to all aspects of
MPI-2, including I/O. It has lots of example programs.

The following papers related to ROMIO are available online:

* Rajeev Thakur, William Gropp, and Ewing Lusk, ``Optimizing
Noncontiguous Accesses in MPI-IO,'' Parallel Computing, (28)1:83--105,
January 2002. 
http://www.mcs.anl.gov/~thakur/papers/mpi-io-noncontig.ps

* R. Thakur, W. Gropp, and E. Lusk, ``On Implementing MPI-IO Portably
and with High Performance,'' in Proc. of the Sixth Workshop on I/O in
Parallel and Distributed Systems, May 1999. 
http://www.mcs.anl.gov/~thakur/papers/mpio-impl.ps

* R. Thakur, W. Gropp, and E. Lusk, ``Data Sieving and Collective I/O
in ROMIO,'' in Proc. of the 7th Symposium on the Frontiers of
Massively Parallel Computation, February 1999, pp. 182--189.
http://www.mcs.anl.gov/~thakur/papers/romio-coll.ps 

* R. Thakur, W. Gropp, and E. Lusk, ``A Case for Using MPI's Derived
Datatypes to Improve I/O Performance,'' in Proc. of SC98: High
Performance Networking and Computing, November 1998.
http://www.mcs.anl.gov/~thakur/dtype

* R. Thakur, W. Gropp, and E. Lusk, ``An Abstract-Device Interface for
Implementing Portable Parallel-I/O Interfaces,'' in Proc. of the 6th
Symposium on the Frontiers of Massively Parallel Computation, 
October 1996, pp. 180-187.
http://www.mcs.anl.gov/~thakur/papers/adio.ps