FAQ about the replication between HFSQL servers
When implementing a replication between HFSQL servers, why are the automatic identifiers coded on 8 bytes?
When the primary key is an automatic identifier, the server must check the uniqueness of the identifiers on all the servers taking part in the replication.
To do so, each replication server uses a range of different values for the automatic identifiers of the created records.
In order for the range of automatic identifiers used by each server to be wide enough, the automatic identifiers must be coded on 8 bytes.
Why are the values of automatic identifiers added once the server replication was implemented so high?
Each server taking part in the replication is using a different range of automatic identifiers based on the identifier of replication server.
The first range of automatic identifiers (the one that starts from 0) will not be used by any server taking part in the replication: this range of identifiers is reserved to the existing data when implementing the first replication.
Therefore, as soon as a new record is created in a server replication, if an automatic identifier is assigned to the file, the value of this identifier will be a high value.
What is the network configuration required to set up server replication?
Server replication uses port 4996 to to transfer data.
- In a bidirectional replication, port 4996 must be open on both servers (master and subscriber).
- In a unidirectional or spare replication, port 4996 can be open only on the subscriber or spare server.
The structure of files was modified in the analysis (addition, modification or deletion of items). How to apply the modifications to the files found on HFSQL servers with a server replication?
All you have to do is apply the modification of structure (automatic data modification) to the master replication server. This automatic data modification can be run:
- from the data model editor,
- when installing the application
- through programming.
During the next data synchronization between servers, the modification of the file structure will be automatically applied to the subscriber HFSQL servers. The stored procedures and the server triggers will also be updated during this synchronization.
Server replication: Are the transactions managed on the HFSQL servers?
When records are modified, added or deleted in transaction on an HFSQL server in replication mode, the records are replicated on the subscriber servers only when the transaction is validated.
If the transaction is canceled (rollback), no replication will be performed for the relevant records.
If the transaction is validated, all the operations in transaction will be transmitted to the replicated servers.
Server replication: What type of security is used for server replication?
The communication between servers is authenticated. It is also encrypted.
Server replication : How are the server triggers run?
A server trigger associated with a file update is run on the HFSQL server for which the function that activates the trigger is called.
All the modified records are synchronized by server replication.
Therefore, if a server trigger makes modifications in the data, these modifications will be automatically applied to the replicated servers without having to run the triggers on the replicated servers.