Question 1

How are files stored in a cluster system?

Accepted Answer

Control files, data files, and log files are stored on each cluster member.
Backup files vary depending on site policy, but typically each group stores a backup file.

Question 2

Does a lock occur on the table when rebalancing?

Accepted Answer

No LOCK is placed on the table on which data rebalancing is being performed.
When a transaction occurs on the table, the transaction
Recorded to disk through journaling, and after rebalancing is completed
This is how journaled transactions are performed.
However, when reflecting the last Journal data (default 10MB), a lock is placed on the table.

Also, depending on the amount of data or table
Since it is not possible to completely avoid system overload,
We recommend that you perform this task during times of relatively low transaction volume.

Question 3

Is it possible to scale in/out during operation? (data distribution and synchronization time, expected load)

Accepted Answer

GOLDILOCKS allows online Scale In/Out.
When a new cluster group is added, the shard data is redistributed accordingly, and this redistribution time varies greatly depending on the amount of data and hardware specifications.
Moving a shard or synchronizing data may cause CPU and network load on the corresponding node.
Also, when processing the last journal data (default 10MB) during the rebalancing process, a table lock is acquired, so it is recommended to perform the work during a time when there are relatively few transactions.

Question 4

Are there any constraints on the sharding key?

Accepted Answer

Primary Key, Unique Constraints, and Unique Index for Shared Tables must include the Sharding Key

Question 5

What columns should the sharding key consist of?

Accepted Answer

How to find the appropriate column for the Sharding Key depends on the query of your application.
It is mainly set as a commonly used join key or a condition key in the where clause.
If you use a composite sharding key, the desired performance may not be achieved.

Question 6

Active - If I use it as Active and then want to use it as Active-Standby, do I need to rebuild the DB?

Accepted Answer

No, you can use it as an Active-Standby just by setting up the Client.
The Goldilocks Cluster is enabled by default as Active-Active.
You can use it as an Active-Standby if you collect clients that perform DML only to one side
In addition, if you are using Global Connection, you can adjust the A-A/A-S with the 'LOCALITY_MEMBER_POLICY' property.

Question 7

Will the Cluster System operate normally when some of the cluster component nodes are terminated?

Accepted Answer

In Goldilocks' Cluster environment, all members within a Group have the same data,
Because it is a Shared Nothing structure, continuous operation is possible through other nodes in case of node failure.

For example, in an environment configured as 1by2, even if a G1N1 device fails,
Failover occurs to G1N2 with the same data.

This is done by gmaster's Failover Thread.
It handles failover, including offline processing for failed nodes and selection of a coordinator.

Coordinator is a concept that ensures data consistency within a cluster system.
It can be viewed as a Master concept responsible for commit/rollback processing.

Question 8

When some of the cluster constituent nodes are shut down, will the Connection automatically failover/will there be a service interruption?

Accepted Answer

Provides automatic failover/failback when configuring a cluster.

In an environment where there are two members for one group (called G1N1 and G1N2),
While establishing a connection/session with G1N1,
If a G1N1 node fails, the glocator or location file is defined
A connection to G1N2 is made using alternative information (G1N2 information).

Also, when recovering G1N1, connections to G1N2 are not automatically moved to the G1N1 node.
In case of a failure of G1N2, the connection to G1N1 proceeds in the same way.
Therefore, atlernative information usually records information about all nodes.

DB service can be operated without interruption.

Question 9

In a cluster configuration, is data access possible when all members of a group fail?

Accepted Answer

If all members of a Group are disabled, the data in that Group becomes inaccessible.
It is only possible to perform queries on data excluding the group in question.

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