Chapter 10. SQL Remote Administration
Issuesto consider Theissues to consider when tuning the message-sending process are similar
tothose when tuning the incoming-message polling frequency:
♦Regularmessages Yourchoices dictate how often updates are sent to
remotedatabases.
♦Resendrequests Whena remote user requests that a message be
resent,the Message Agent needs to take special action that can interrupt
regularmessage sending. Youcan control the urgency with which these
resendrequests are processed.
♦Numberand siz e of messages Ifyou send messages veryfrequently,
thereis more chance of small messages being sent. Sendingmessages
lessfrequently allows more instructions to be grouped in a single
message. If a large number of small messages is a concern for your
messagesystem, then you may have to avoid using very small polling
periods.
☞Formore information on tuning polling for the incoming-messages, see
“Tuningincoming message polling” on page 230.
Pollinginterval
Youcontrol the interval to wait between polls for more data from the
transactionlog to send using the -sd option, which has a default of one
minute. The following example sets the polling intervalto 30 seconds:
dbremote -sd 30s ...
Alternatively,you can poll less frequently, as in the following command line,
whichpolls every five minutes:
dbremote -sd 5
Settinga very small interval may have some detrimental impact on overall
systemthroughput, for the following reasons:
♦Too-frequentpolling produces many short messages. If the message load
placesa strain on your message system, throughput could be affected.
Settinglarger intervals may provide a better overall throughput of messages
inyour system, at the cost of waiting somewhat longer for each message to
beapplied. Inmany SQL Remote installations, optimizing turnaround time
isnot the primary concern.
Resending messages
Whena user requests that a message be resent, the message has to be
retrievedfrom early in the transaction log. Goingback in the transaction log
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