lockng.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: lockng.so,v 1.6 2004/09/28 14:13:09 bostic Exp $])

m4_ref_title(Upgrading m4_db Applications,
    Release 4.2: DB_LOCK_NOTGRANTED,,
    upgrade.4.2/verify, upgrade.4.2/repinit)

m4_p([dnl
In previous releases, configuring lock or transaction timeout values or
calling the m4_refT(txn_begin) with the m4_ref(DB_TXN_NOWAIT) flag
caused database operation methods to return m4_ref(DB_LOCK_NOTGRANTED),
or throw a m4_refcxx(DbLockNotGrantedException) exception.  This
required applications to unnecessarily handle multiple errors or
exception types.])

m4_p([dnl
In the m4_db 4.2 release, with one exception, database operations will
no longer return m4_ref(DB_LOCK_NOTGRANTED) or throw a
m4_refcxx(DbLockNotGrantedException) exception.  Instead, database
operations will return m4_ref(DB_LOCK_DEADLOCK) or throw a
m4_refcxx(DbDeadlockException) exception.  This change should require
no application changes, as applications must already be dealing with the
possible m4_ref(DB_LOCK_DEADLOCK) error return or
m4_refcxx(DbDeadlockException) exception from database operations.])

m4_p([dnl
The one exception to this rule is the m4_ref(dbh_get) method using the
m4_ref(DB_CONSUME_WAIT) flag to consume records from a Queue.  If lock
or transaction timeouts are set, this method and flag combination may
return m4_ref(DB_LOCK_NOTGRANTED) or throw a
m4_refcxx(DbLockNotGrantedException) exception.])

m4_p([dnl
Applications wanting to distinguish between true deadlocks and timeouts
can configure database operation methods to return
m4_ref(DB_LOCK_NOTGRANTED) or throw a
m4_refcxx(DbLockNotGrantedException) exception using the
m4_ref(DB_TIME_NOTGRANTED) flag.])

m4_p([dnl
The m4_ref(lock_get) and  m4_refT(lock_vec)s will continue to return
m4_ref(DB_LOCK_NOTGRANTED), or throw a
m4_refcxx(DbLockNotGrantedException) exception as they have previously
done.])

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