Chapter 12. Administering SQL Remote for AdaptiveSer ver
Enterprise
Making schema changes
Schemachanges to tables being replicated by SQL Remote must be made on
aquietsystem. Aquiet system means the following:
Notransactions being replicated Therecan be no transactions being
replicatedthat modify the tables that are to be altered. Alltransactions
thatmodify tables being altered must be scanned from the transaction log
intothe stable queue before the schema is altered. Thisis performed by
runningthe Message Agent normally, or using the -I -b options. After
theMessage Agent completes, you can make the schema change.
MessageAg ent TheMessage Agent must be shut downwhen the
schemachange is being made.
SQLRemote Open Ser ver Ifyou are using the SQL Remote Open
Server,it must be shut down when the schema change is being made.
Schemachanges include changes to publications, such as adding articles or
modifyingarticles. However,creating or dropping subscriptions, and adding
orremoving remote users do not need to be done on a quiet system.
Inthe Adaptive Server Enterprise transaction log, there is no information
recordingtable structure changes: theSQL Remote log scanning process
getsthe table structure from the Adaptive Server Enterprise system tables.
Consequently,the Message Agent cannot scan an operation from the
transactionlog that happened against the old table structure.
Informationstored in the stable queue before the schema change uses the old
tabledefinitions and information stored after the schema change uses the
newtable definitions.
Passthroughmode can be used at the same time as the schema change to
makesure that schema changes at remote databases occur in the correct
sequence.
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