If you use Derby's in-memory database facility, it is important to configure the following:

• The size of the Java heap. The memory requirements for an in-memory database should be similar to the memory requirements for using the file system, plus the size of the user data.
• The Derby page cache size. For good performance, use no less than the default size of 1000 pages. The data must pass through the page cache, even though the user data is already stored in main memory. A larger page cache may improve performance at the expense of increased memory usage. See Increase the size of the data page cache for more information.

If you want to prevent Derby from writing anything to the derby.log file, use one of the derby.stream.error properties (for instance, derby.stream.error.field).

For more information, see "Using in-memory databases" in the Derby Developer's Guide.