HP OpenView Storage Mirroring User Guide (360226-002, May 2004)

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How Replication Sets Work

To better understand how replication sets work, the following diagram identifies the steps involved with creating and saving

a replication set as well as what happens to the replication set information after a source and target have been connected.

Each numbered step is described following the diagram.

1. The Storage Mirroring client manages all replication set modifications. The administrator creates, modifies, or deletes

replication set rules or the replication set itself from the Storage Mirroring client machine.

2. The first time a replication set is saved, the replication set database, Dbltake.db, is created on the source machine.

This file contains all of the replication sets that are established for that machine.

3. When the Storage Mirroring client manages any replication set activity after the initial creation of Dbltake.db, the

source machine sends the entire file to the client machine.

4. When the administrator modifies a replication set, the Storage Mirroring client manages that activity and modifies the

local copy of

Dbltake.db.

5. When the replication set is saved, the Dbltake.db file is sent to the source machine.

6. When a source/target connection is established, a portion of the replication set database is sent to the target machine.

The portion contains only the data that is relevant to the current connection; it does not contain replication set data

that is relevant to other connections. The file on the target machine is identical to the source machine’s name so that the

file can be recovered if the source machine crashes. It is called

source_machine_name.db.

Multi-Client Access

Replication sets contain error checking to avoid inadvertent overwrites of the Dbltake.db file. When Dbltake.db is

retrieved from the source to the client, a generation number is associated with the retrieval. The generation number is

incremented anytime there are successful changes to

Dbltake.db. When attempting to save a replication set, the generation

numbers on the source and client are compared and if they are different, the save is not allowed. The Storage Mirroring

Management Console will prompt you if the replication set cannot be saved. This error checking safeguards the replication

set data in the event that more than one client machine is accessing the source machine’s replication sets.

Source

Target

SourceMachine.db

Replication Set 1

Replication Set 2

Replication Set 3