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SQL Anywhere 12.0.0 (Français) » SQL Anywhere Server - Database Administration » Maintaining your database » SQL Anywhere high availability » Introduction to database mirroring » Choosing a database mirroring mode

 

State information files

Each server in the mirroring system maintains a state information file that records that server's view of the state of the mirroring system.

The state information file is used during startup when determining the role to be assumed by a server. The server's local state is compared against that of the other servers in the database mirroring system.

You must always specify a state information file for each server in the mirroring system using the state_file option of the CREATE MIRROR SERVER statement. See CREATE MIRROR SERVER statement.

The state information file contains the following information:

Field Description
Owner Indicates which database server is the primary server.
State Contains the synchronization state (one of synchronizing or synchronized) to indicate whether the server is receiving log pages or is up to date. See Synchronization states.
Mode Specifies the synchronization mode (one of synchronous, asynchronous, or page). See Choosing a database mirroring mode.
Sequence Contains a value indicating how many times failover has occurred on the database mirroring system. The sequence number is incremented on each role switch. It helps to determine whether a server's view of the state of the mirroring system is current. See Introduction to database mirroring.

The following shows sample contents for a state information file:

[demo]
Owner=server2
State=synchronizing
Mode=asynchronous
Sequence=35

If a state information file does not exist, it is created automatically. State information files should only be modified by the database server.