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HowTo - Put the database in maintenance mode

Environment

Pivotal Greenplum Database all releases.

Goal

How do you put the database in "maintenance mode", for example required when you need to run gpcheckcat?

By "maintenance mode" here we mean: editing "pg_hba.conf" to limit connections and using restricted mode at the same time.

Solution

  • Enable local connections by gpadmin only. The IP address 172.28.8.250 is the default address responding to the master node mdw from servers within a DCA, please change it accordingly if it's not a DCA by pinging the master node locally from the master node itself (via its host name) to see what IP address is resolved to. In this example:
# mv -i $MASTER_DATA_DIRECTORY/pg_hba.conf $MASTER_DATA_DIRECTORY/pg_hba.conf.$(date +%Y%m%d)
# echo -e "local all gpadmin ident\nhost all gpadmin 127.0.0.1/28 trust\nhost all gpadmin 172.28.8.250/32 trust" > $MASTER_DATA_DIRECTORY/pg_hba.conf
# gpstop -u
  • Check if the database is in restricted mode:
# pgrep -fl silent
  • If it is in restricted mode, you will see "-c superuser_reserved_connections=" in the postmaster command string (max_connections is set to 250 by default on master).
  • Otherwise restart the database in restricted mode:
# gpstop -M fast
# gpstart -R
  • Remember to restore the original pg_hba.conf and restart the db in normal mode at the end of the activity.

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