hdf5/doc/VFD_SWMR_Guide.md

VFD SWMR User's Guide

Caveats

A few library functions are known to work incorrectly with VFD SWMR.

• Variable-length data written using VFD SWMR may be inaccessible or inconsistent to a VFD SWMR reader until the writer closes the file. Instead of the proper variable-length data, a reader may read NULL or arbitrary bytes. Inconsistencies may also cause the reader to crash.

• Applications should take care using HDF5 iteration APIs, especially when iterating large numbers of objects or using long-running application callbacks. While the library is in an iteration routine, it does not track changes made by the writer. If the library spends more than max_lag ticks in the routine, then its view of the HDF5 file will become stale. Under those circumstances, HDF5 content could be mis-read, or the library could crash with a diagnostic assertion.

• At the present level of development, the writer cannot invalidate a reader's HDF5 object handles (hid_ts). If a reader holds an object open---that is, it has a valid handle (hid_t) for the object---while the writer deletes it, then reading content through the handle may yield corrupted data or the data from some other object, or the library may crash.