This page describes operations that impact availability in Cloud SQL.

Cloud SQL helps you maximize the uptime of your database without any
changes to your application. With a 99.99% uptime [SLA](https://cloud.google.com/sql/sla) and
near-zero downtime for several planned operations,
Cloud SQL Enterprise Plus edition offers greater resilience and business continuity for your
applications.

Maximizing uptime means reducing the downtime for your database.
Downtime is typically caused by both unplanned events and planned operations.

## Unplanned events and zonal outage

For applications that require high availability, we recommend configuring
the instance for regional availability, also referred to as the
high availability (HA) configuration in Cloud SQL.
For more information about configuring high availability in Cloud SQL, see
[About high availability (HA)](https://docs.cloud.google.com/sql/docs/postgres/high-availability.md.txt).

For instances configured with regional availability, if the instance
encounters a failure, then Cloud SQL automatically brings up the
instance in the secondary zone with the same IP address and
no data loss so that applications can resume operations on the database.
This protects against unplanned events such as the failure of a single VM
host, or the failure of one or more infrastructure components that causes
the outage of an entire zone.

Cloud SQL high availability is available for both Cloud SQL Enterprise Plus edition and
Cloud SQL Enterprise edition.

If you don't configure regional availability for an instance, then the instance
is configured for zonal availability, also referred to as a
standalone instance.

Cloud SQL recovers standalone instances (instances configured with zonal availability)
from VM host failures automatically.
However, Cloud SQL doesn't recover standalone instances from a zonal
outage automatically. To re-establish a standalone instance in a healthy zone,
you must restore any standalone instances manually.
You can recover a standalone instance from a zonal outage manually by
performing either point-in-time-recovery or by promoting a read replica to
become the standalone instance. For more information, see
[Recovery options for standalone instances](https://docs.cloud.google.com/sql/docs/postgres/high-availability.md.txt#recovery-options).

## Planned operations with near-zero downtime

For planned operations such as maintenance or some instance reconfigurations,
Cloud SQL Enterprise Plus edition offers near-zero downtime for
primary instances with no application changes or proxy requirements.

The following planned operations benefit from the near-zero downtime
on a Cloud SQL Enterprise Plus edition primary instance. These downtimes are applicable to
both standalone (zonal) and high availability (regional) instances.

- [Maintenance](https://docs.cloud.google.com/sql/docs/postgres/maintenance.md.txt#nearzero), which includes the
  following operations with sub-second downtime:

  - Automatic maintenance that Cloud SQL performs every quarter
  - Self-service maintenance that you can initiate at any time
  - Maintenance simulation that you can initiate to test the sub-second downtime behavior

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- Minor version upgrade
  - Minor version upgrades are part of automatic maintenance and happen with sub-second downtime

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- [Edition upgrade](https://docs.cloud.google.com/sql/docs/postgres/upgrade-cloud-sql-instance-to-enterprise-plus-in-place)

  - Perform an in-place upgrade to Cloud SQL Enterprise Plus edition
- Enable [data cache](https://docs.cloud.google.com/sql/docs/postgres/data-cache.md.txt)

  - You can enable or disable data cache as frequently as needed
- Instance scaling

  - Scale-up: Increase the compute size (vCPU, memory) of your Cloud SQL instance as frequently as needed
  - Scale-down: Reduce the compute size (vCPU, memory) of your
    Cloud SQL instance infrequently

    > [!NOTE]
    > **Note:** If you scale down your instance more than once during a three-hour period, then only the first scale down event benefits from near-zero downtime. Subsequent scale down events experience regular downtime.

## What's next

- Learn [about high availability (HA)](https://docs.cloud.google.com/sql/docs/postgres/high-availability.md.txt)

- [Enable or disable high availability (HA)](https://docs.cloud.google.com/sql/docs/postgres/configure-ha.md.txt)

- Read [about disaster recovery (DR)](https://docs.cloud.google.com/sql/docs/postgres/intro-to-cloud-sql-disaster-recovery.md.txt)

- View all the [Google Cloud services available in locations worldwide](https://cloud.google.com/about/locations).