m4_comment([$Id: db_close.so,v 10.55 2004/08/13 03:38:55 bostic Exp $])

define(M4PAGELOCAL, dbh_close)
include(m4/m4.seealso)

m4_pf_header(m4_ref(dbh_close),
ifelse(M4API, C_API, [dnl
int
DB-__GT__close(DB *db, u_int32_t flags);
])
ifelse(M4API, CXX_API, [dnl
int
Db::close(u_int32_t flags);
]))

m4_p([dnl
The m4_refT(dbh_close) flushes any cached database information to disk,
closes any open cursors, frees any allocated resources, and closes any
underlying files.])

m4_p([dnl
The m4_ref(Db) handle should not be closed while any other handle that
refers to it is not yet closed; for example, database handles must not
be closed while cursor handles into the database remain open, or
transactions that include operations on the database have not yet been
committed or aborted.  Specifically, this includes m4_ref(Dbc) and
m4_ref(DbTxn) handles.])

m4_p([dnl
Because key/data pairs are cached in memory, failing to sync the file
with the m4_ref(dbh_close) or m4_refT(dbh_sync) may result in
inconsistent or lost information.])

m4_p([dnl
When called on a database that is the primary database for a secondary
index, the primary database should be closed only after all secondary
indices which reference it have been closed.])

m4_p([dnl
When multiple threads are using the m4_ref(Db) concurrently, only a single
thread may call the m4_refT(dbh_close).])

m4_destructor(Db, dbh_close)

m4_return(dbh_close, std)

m4_parambegin
m4_param(flags, [dnl
m4_sf_or_may

m4_tagbegin
m4_tag(m4_idef(DB_NOSYNC), [dnl
Do not flush cached information to disk.  The m4_ref(DB_NOSYNC) flag is
a dangerous option.  It should be set only if the application is doing
logging (with transactions) so that the database is recoverable after
a system or application crash, or if the database is always generated
from scratch after any system or application crash.
m4_p([m4_bold([dnl
It is important to understand that flushing cached information to disk
only minimizes the window of opportunity for corrupted data.]) Although
unlikely, it is possible for database corruption to happen if a system
or application crash occurs while writing data to the database.  To
ensure that database corruption never occurs, applications must either:
use transactions and logging with automatic recovery; use logging and
application-specific recovery; or edit a copy of the database, and once
all applications using the database have successfully called
m4_ref(dbh_close), atomically replace the original database with the
updated copy.])])

m4_tagend])
m4_paramend

m4_err(dbh_close, einval)

m4_seealso(Db)
m4_page_footer