#include <db_cxx.h> int DbEnv::set_memory_max(roff_t size);
This method sets the maximum amount of memory to be used by shared
structures in the main environment region. These are the
structures used to coordinate access to the environment other than
mutexes and those in the page cache (memory pool). If the region
files are in memory mapped files, or if
DB_PRIVATE is specified, the memory specified by
this method is not allocated completely at startup. As memory is
needed, the shared region will be extended or, in the case of
DB_PRIVATE, more memory will be allocated using
the system malloc call. For memory mapped files, a mapped region
will be allocated to this size but the underlying file will only be
allocated sufficient memory to hold the initial allocation of
shared memory structures as set by
DbEnv::set_memory_init().
If no memory maximum is specified then it is calculated from
defaults, initial settings or (deprecated) maximum settings of the
various shared structures. In the case of environments created
with DB_PRIVATE, no maximum need be set and the
shared structure allocation will grow as needed until the process
memory limit is exhausted.
The database environment's maximum memory may also be configured using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "set_memory_max", one or more whitespace characters, followed by the maximum to be allocated. Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.
The DbEnv::set_memory_max() method must be
called prior to opening the database environment.
The DbEnv::set_memory_max()
method may fail and throw a DbException
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
If the method was called after DbEnv::open() was called; or if an invalid flag value or parameter was specified.