u_int32_t gbytes, u_int32_t bytes, int ncache);
Set the size of the database's shared memory buffer pool, i.e., the cache,
to gbytes gigabytes plus bytes. The cache should be the
size of the normal working data set of the application, with some small
amount of additional memory for unusual situations. (Note, the working
set is not the same as the number of simultaneously referenced pages, and
should be quite a bit larger!)
The default cache size is 256KB, and may not be specified as less than
20KB. Any cache size less than 500MB is automatically increased by 25%
to account for buffer pool overhead, cache sizes larger than 500MB are
used as specified. For information on tuning the Berkeley DB cache size, see
Selecting a cache size.
It is possible to specify caches to Berkeley DB that are large enough so that
they cannot be allocated contiguously on some architectures, e.g., some
releases of Solaris limit the amount of memory that may be allocated
contiguously by a process. If ncache is 0 or 1, the cache will
be allocated contiguously in memory. If it is greater than 1, the cache
will be broken up into ncache equally sized separate pieces of
As databases opened within Berkeley DB environments use the cache specified to
the environment, it is an error to attempt to set a cache in a database
created within an environment.
The DB->set_cachesize interface may only be used to configure Berkeley DB before
the DB->open interface is called.
The DB->set_cachesize function returns a non-zero error value on failure and 0 on success.