RE: Max_connections limit

From: Daulat Ram [mailto:Daulat(dot)Ram(at)exponential(dot)com]
Sent: Wednesday, June 26, 2019 3:14 AM
To: pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: Max_connections limit

Hello team,

We have migrated our database from Oracle 12c to Postgres 11. I need your suggestions , we have sessions limit in Oracle = 3024 . Do we need to set the same connection limit in Postgres as well. How we can decide the max_connections limit for postgres. Are there any differences in managing connections in Oracle and postgres.

SQL> show parameter sessions;

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
java_max_sessionspace_size integer 0
java_soft_sessionspace_limit integer 0
license_max_sessions integer 0
license_sessions_warning integer 0
sessions integer 3024
shared_server_sessions integer
SQL>

Regards,
Daulat

The difference between Oracle and PG is that Oracle has "built-in" connection pooler, and PG does not.
You should use external pooler (i.e. PgBouncer) and reduce number of allowed connections in PG config to about 50, while allowing thousands client connection when configuring PgBouncer.

Regards,
Igor Neyman