# 3.4. General Run-Time Support Notes

- The PMIx installation must be in your `PATH` on all nodes (and potentially `LD_LIBRARY_PATH` or `DYLD_LIBRARY_PATH`, if `libpmix` is a shared library).

- PMIx’s run-time behavior can be customized via Modular Component Architecture (MCA) parameters (see the MCA section for more information on how to get/set MCA parameter values).

- If specified, we recommend that the `ptl_tcp_if_include` parameter include the loopback device (`lo` on many Linux platforms) to ensure that at least one intra-node transport can be found between a local client and its server. For example: `export PMIX_MCA_ptl_tcp_if_include lo,eth1 ...`

- Running on nodes with different endian and/or different datatype sizes within a single PMIx-based application is supported in this release, at least from a PMIx perspective (i.e., we will pack/unpack to handle the situation). However, PMIx does not resize data when the same datatype differs in size (for example, sending a 4 byte `double` and receiving an 8 byte `double` will fail).