perThreadHardLimitMB

Expert: Sets the maximum memory consumption per thread triggering a forced flush if exceeded. A DocumentsWriterPerThread is forcefully flushed once it exceeds this limit even if the .getRAMBufferSizeMB has not been exceeded. This is a safety limit to prevent a [ ] from address space exhaustion due to its internal 32 bit signed integer based memory addressing. The given value must be less that 2GB (2048MB)

See also