Greenplum Database Backend Server Programs corresponding to PostgreSQL

Greenplum Database is based on PostgreSQL 8.2.15 but Greenplum uses a different process /commands used in PostgreSQL.

1. initdb: This program is called by gpinitsystem when initializing a Greenplum Database array. It is used internally to create the individual segment instances and the master instance.(Greenplum usesgpinitsystem).

Note: ipcclean which is used in PostgreSQL is not used in Greenplum database.

2. gpsyncmaster: This is the Greenplum program that starts the gpsyncagent process on the standby master host. Administrators do not call this program directly, but do so through the management scripts that initialize and/or activate a standby master for a Greenplum Database system. This process is responsible for keeping the standby master up to date with the primary master via a transaction log replication process.(used insteadgpinitstandby, gpactivatestandby).

Note : pg_controldata which is used in PostgreSQL is not used in Greenplum Database (Greenplum uses: gpstate)

3. pg_ctl: This program is called by gpstart and gpstop when starting or stopping a Greenplum Database array. It is used internally to stop and start the individual segment instances and the master instance in parallel and with the correct options.
(Greenplum uses: gpstart, gpstop)

Note: pg_resetxlog which is used in PostgreSQL is not  used in Greenplum Database

4. postgres: The postgres executable is the actual PostgreSQL server process that processes queries. (Greenplum uses: The main postgres process (postmaster) creates other postgres subprocesses and postgres session as needed to handle client connections.)

5. postmaster: postmaster starts the postgres database server listener process that accepts client connections. In Greenplum Database, a postgres database listener process runs on the Greenplum Master Instance and on each Segment Instance.(Greenplum uses: In Greenplum Database, you use gpstart and gpstop to start all postmasters (postgres processes) in the system at once in the correct order and with the correct options.)
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