Cisco Cisco Access Registrar 3.5 - Manual (Page 44)

4-6
Cisco Access Registrar 3.5 Concepts and Reference Guide
OL-2683-02
Chapter 4 Understanding Replication
Replication Configuration Settings
RepType
RepType indicates the type of replication. The choices available are SMDBR and NONE.
When RepType is set to NONE, replication is disabled. To enable replication, set RepType to SMDBR
for Single Master DataBase Replication. RepType must be set to SMDBR on both the master and slave
servers.
RepTransactionSyncInterval
Master
On the master server, RepTransactionSyncInterval is the duration between periodic transmission of the
TransactionSync message expressed in milliseconds. The default is 60000 or 1 minute.
The purpose of RepTransactionSyncInterval is to indicate how frequently to check for an out-of -sync
condition between the master and slave servers. When the slave received the TransactionSync message,
it uses its contents to determine if it needs to resynchronize with the master.
The larger the setting for RepTransactionSyncInterval, the longer the period of time between out-of-sync
detection. However, if RepTransactionSyncInterval is set too small, the slave may frequently request
resynchronization when it is not really out of sync. If the duration is too small, the slave cannot
completely receive a transaction before it receives the TransactionSync message. In this case, the servers
will remain synchronized, but there will be unnecessary excess traffic that could affect performance.
Slave
On the slave, RepTransactionSyncInterval is used to determine if the slave has lost contact with the
master and to alert administrators of a possible loss of connectivity between the master an slave. If the
elapsed time since the last received TransactionSync message exceeds the setting of
RepTransactionSyncInterval, the slave writes a log message indicating that it may have lost contact with
the master. This log message is repeated each TransactionSyncInterval until a TransactionSync message
is received.
RepTransactionArchiveLimit
On both master and slave, the RepTransactionArchiveLimit setting determines how many transactions
can be stored in the archive. The default setting is 100. When the limit is exceeded, the oldest transaction
file is deleted. If a slave requires resynchronization and the last transaction it received is no longer in the
archive, a full resynchronization will be necessary to bring the slave back in sync with the master.
Note The value set for RepTransactionArchiveLimit should be the same on the master and the slave.
An appropriate value for RepTransactionArchiveLimit depends upon how much hard disk space an
administrator can provide for resynchronization. If this value is large, say 10,000, then the last 10,000
transactions will be stored in the archive. This is like saying the last 10,000 saves from aregcmd will be
stored in the archive. Large values are best. The size of each transaction depends upon how many
configuration changes were included in the transaction, so hard disk space usage is difficult to estimate.