config.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: config.so,v 10.19 2002/07/22 05:11:58 bostic Exp $])

m4_ref_title(Transaction Subsystem,
    Configuring transactions, @transaction configuration, txn/intro, txn/limits)

m4_p([dnl
The application may change the number of simultaneous outstanding
transactions supported by the m4_db environment by calling the
m4_refT(dbenv_set_tx_max).  This will also set the size of the
underlying transaction subsystem's region.  When the number of
outstanding transactions is reached, additional calls to
m4_ref(txn_begin) will fail until some active transactions complete.])

m4_p([dnl
There is an additional parameter used in configuring transactions; the
m4_ref(DB_TXN_NOSYNC) flag.  Setting the m4_ref(DB_TXN_NOSYNC) flag to
m4_ref(dbenv_set_flags) when opening a transaction region changes the
behavior of transactions to not write or synchronously flush the log
during transaction commit.])

m4_p([dnl
This change may significantly increase application transactional
throughput.  However, it means that although transactions will continue
to exhibit the ACI (atomicity, consistency, and isolation) properties,
they will not have D (durability).  Database integrity will be
maintained, but it is possible that some number of the most recently
committed transactions may be undone during recovery instead of being
redone.])

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