Greenplum DCA - Quick facts


1. The master is the entry point to the Greenplum Database system. It is the database process that accepts client connections and processes SQL commands that system users issue.
segment, and presents the final results to the client program.

Standby Master server specification is same as master.

1. Standby Master is configured as WARM Standby.

Quick facts about Greenplum Database Segment Servers
1. Segments are where data is stored and the majority of query processing takes place. 
2. When a user connects to the database and issues a query, processes are created on each segment to handle the work of that query.
4. In the recommended Greenplum Database hardware configuration, there is one active segment per effective CPU or CPU core. For example, if your segment hosts have two dual-core processors, you would have four primary segments per host.
5. The segments communicate with each other and with the master over the interconnect, which is the networking layer of Greenplum Database.
6. The Greenplum primary and mirror segments are configured to use different interconnect switches in order to provide redundancy in the event of a single switch failure.
7. Greenplum Database provides data redundancy by deploying mirror segments. Mirror segments allow database queries to fail over to a backup segment if the primary segment becomes unavailable.
8. A mirror segment always resides on a different host than its corresponding primary segment. 
9. A Greenplum Database system can remain operational if a segment host, network interface or interconnect switch goes down as long as all portions of data are available on the remaining active segments.
10. During database operations, only the primary segment is active.
11. Changes to a primary segment are copied over to its mirror using a file block replication process. Until a failure occurs on the primary segment, there is no live segment instance running on the mirror host -- only the replication process.
12. In the event of a segment failure, the file replication process is stopped and the mirror segment is automatically brought up as the active segment instance. All database operations then continue using the mirror. While the mirror is active, it is also logging all transactional changes made to the database. When the failed segment is ready to be brought back online, administrators initiate a recovery process to bring it back into operation.

Each segment instance have their own postgresql.conf file. Some parameters are local. each segment instance examines its own postgresql.conf file to
get the value of that parameter. 

To change a local configuration parameter across multiple segments, update the parameter in the postgresql.conf file of each targeted segment, both primary and
mirror. Use the gpconfig utility to set a parameter in all Greenplum postgresql.conf files. For example: 
$gpconfig -c gp_vmem_protect_limit -v 4096MB

Greenplum Interconnect

1. The interconnect is the networking layer of Greenplum Database. 
3. The Greenplum interconnect uses a standard Gigabit Ethernet switching fabric.
4. By default, the interconnect uses User Datagram Protocol (UDP) to send messages over the network. 
8. To maximize throughput, interconnect activity is load-balanced over two interconnect networks. 
9. To ensure redundancy, a primary segment and its corresponding mirror segment utilize different interconnect networks. With this configuration, Greenplum
Database can continue its operations in the event of a single interconnect switch failure.

ConnectEMC Event Alerts for Interconnect
Code       Description
14.12002 Interconnect Switch Operational Status.
14.12005 Operational status of Interconnect switch flash memory.
14.12006 State of Interconnect switch flash memory.