Adaptive Server Enterprise transaction log andbackup management
Youmust protect against losing transactions that have been replicated to
remotedatabases. Iftransactions are lost that have already been replicated to
remotedatabases, the remote databases will be inconsistent with the
consolidateddatabase. Inthis situation, you may have to re-extract all
remotedatabases.

Protecting against media failure on the transaction log

Mediafailure on the transaction log can cause committed transactions to be
lost. If the transaction log has been scanned and these transactions have
alreadybeen sent to subscriber databases, then the subscribing databases
containtransactions that are lost from the publishing database, and the
databasesare in an inconsistent state.
Whythe transaction log
isneeded Thetransaction log is needed, even after the entries have been scanned into
thestable queue, to guard against media failure on the database file. Ifthe
databaseis lost, it must be recovered to a point that includes every
transactionthat may have been sent to remote databases.
Thisrecovery is done by restoring a database dump and loading transaction
dumpsto bring the database up todate. The last transactiondump restored is
thedump of the active transaction log at the time of the failure.
Protectingagainst
transactionlog loss Thereare two ways of protecting against inconsistency arising from media
failureon the transaction log:
Mirrorthe transaction log Whena device is mirrored, all writes to the
deviceare copied to a separate physical device.
Onlyreplicate backed-up transactions Thereis a command-line
optionfor the Message Agent that prevents it from sending transactions
untilthey are backed up.
Mirroring the transaction
log Theonly way to protect against media failure on the transaction log is by
mirroringthe transaction log.
Diskmirroring can provide nonstop recovery in the event of media failure.
Thedisk mirror command causes an Adaptive Server Enterprise database
deviceto be duplicated—that is, all writes to the device are copied to a
separatephysical device. Ifone of the devices fails, the other contains an
up-to-datecopy of all transactions.
Forinformation on disk mirroring in Adaptive Server Enterprise, see the
chapter“Mirroring Database Devices”, in the Adaptive Server Enterprise
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