Maker

MapDB detects unclean shutdown (and possible data corruption) by Header Checksum. This checksum becomes invalid if store was modified, but not closed correctly. In that case MapDB will throw an exception and will refuse to open the store.

Enables store wide checksum. Entire file is covered by 64bit checksum to catch possible data corruption. This could be slow, since entire file is traversed to calculate checksum on store open, commit and close.

Adds JVM shutdown hook and closes DB just before JVM;

Adds JVM shutdown hook and closes DB just before JVM. This is similar to closeOnJvmShutdown(), but DB is referenced with WeakReference from shutdown hook and can be GCed. That might prevent memory leaks under some conditions, but does not guarantee DB will be actually closed.

WARNING: this option is dangerous. With locks disabled multi-threaded access could cause data corruption and causes. MapDB does not have fail-fast iterator or any other means of protection

This value has to be power of two, so it is rounded up automatically.

Enables background executor

Enable FileChannel access. By default MapDB uses {@link java.io.RandomAccessFile}. whic is slower and more robust. but does not allow concurrent access (parallel read and writes). RAF is still thread-safe but has global lock. FileChannel does not have global lock, and is faster compared to RAF. However memory-mapped files are probably best choice.

You may experience {@code java.lang.OutOfMemoryError: Map failed} exception on 32bit JVM, if you enable this mode.

Enable Memory Mapped Files only if current JVM supports it (is 64bit).

Open store in read-only mode. Any modification attempt will throw UnsupportedOperationException("Read-only")