Chapter 10. SQL Remote Administration
enablerecovery of data from system or media failure. Ina replication
installation,even if such recovery is achieved, the recovered database can be
outof synch with remote databases. Thiscan require a complete
resynchronizationof remote databases, which can be a formidable task if the
installationinvolves large numbers of databases.
Inshort, recovery of the consolidated database from a failure at the
consolidatedsite is only part of the task of recovering the entire replication
installation.
Protectionof the replication system against media failures has two aspects:
♦Backupand log management Solidbackup procedures and log
managementprocedures for the consolidated database server are an
essentialpart of recovery plans. Backupprocedures protect against media
failureon the database device. Usinga transaction log mirror protects
againstmedia failure on the transaction log device.
☞Formore information about backup and log management procedures,
seethe sections “Transaction log and backup management” on page 249
and“Adaptive Server Enterprise transaction log and backup
management”on page 272.
♦MessageAg ent configuration TheMessage Agent command-line
optionsprovide ways for you to tune Message Agent behavior to match
yourbackup and recovery requirements.
MessageAgent configuration is discussed in the following pages.
Replicatingonly
backed-uptransactions Bydefault, the Message Agent processes all committed transactions. When
theMessage Agent is run with the -u option, only transactions that have
beenbacked up by the database backup commands are processed.
ForAdaptive Server Anywhere, transaction log backup is carried out using
SybaseCentral or the
dbbackup
utility,or off-line copying and renaming of
thelog file. ForAdaptive Server Enterprise, transaction log backup is carried
outusing the dumptransaction statement.
Bysending only backed-up transactions, the replication installation is
protectedagainst media failure on the transaction log. Maintaininga
mirroredtransaction log also accomplishes this goal.
The-u option provides additional protection against total site failure, if
backupsare carried out to another site.
Ensuring consistent Message Agent settings
SomeMessage Agent settings need to be the same throughout an
installation,and so should be set before deployment. Thissection lists the
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