OSF DCE Administration Guide--Core Components

OSF DCE Administration Guide—Core Components
Figure 27-4. Slave Replica Update Process
Registry
Database
Disk Memory
Log File
Replica List
Slave
Security
Server
Replica List
machineA update 1
machine B update 1
.
.
.
Update 1
Update 2
.
.
.
Registry
Database
The server applies
the update to virtual
memory. Periodically,
the server writes the
database in virtual
memory to disk.
The server stores a copy of
each update in the log file.
This file is used in the event of
a server restart to apply all out-
standing updates to the disk
copy of the database.
Database Update
For each replica in the
cell, the replica list con-
tains the replica’s net-
work address, network
ID, and cell–relative
name.
Log File
27.6.2 Handling Database Updates
When a master or slave replica receives updates, it applies the updates to its database in
virtual memory, and saves a copy of each update in a log file that is stored on disk.
Updates accumulate in the log file in sequenced numerical order. If a server restarts
unexpectedly, the log file ensures that no updates are lost.
Periodically, the replica writes the database in virtual memory to disk, thus bringing the
disk copy up-to-date. Then, if the replica is a slave, it clears the log file of all updates. If
the replica is the master, it clears the log file of all updates that have been propagated to
the slave replicas. Updates that have not been propagated to the slaves are retained and
used to reconstruct the propagation queue, if necessary.
Only the master replica maintains a propagation queue, which is used to hold changes to
be propagated to the slave replicas, as described in Section 27.6.3. When the master
replica receives an update, it adds it to the propagation queue in addition to its virtual
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