---
name: databases-for-mysql-howto-changing-config
title: Changing your deployment configuration
description: IBM Cloud® Databases for MySQL allows you to change some of the MySQL configuration settings so you can tune your MySQL databases to your use case. To make permanent changes to the database configuration, use the Cloud Databases CLI-plugin or API to write the changes to the configuration file for your deployment.
last-updated: 2025-12-16
---

> ## Documentation Index
> The table of contents for this documentation set is at https://cloud.ibm.com/docs/databases-for-mysql?format=markdown
> The index for all IBM Cloud docs is at: https://cloud.ibm.com/docs/llms.txt
> Use these files to discover more information as needed.

# Changing your deployment configuration
{: #changing-configuration}

IBM Cloud® Databases for MySQL allows you to change some of the MySQL configuration settings so you can tune your MySQL databases to your use case. To make permanent changes to the database configuration, use the Cloud Databases [CLI-plugin](https://cloud.ibm.com/docs/databases-cli-plugin?topic=databases-cli-plugin-cdb-reference&format=markdown#deployment-configuration) or [API](https://cloud.ibm.com/apidocs/cloud-databases-api#change-your-database-configuration) to write the changes to the configuration file for your deployment.

The configuration is defined in a schema. To make a change, send a JSON object with the settings and their new values to the API or the CLI. For example, in the CLI or API, set the `max_connections` to 150 using a command like:

```sh
{"configuration":{"max_connections":150}}
```
{: .codeblock}

For more information, see [Managing MySQL Connections](https://cloud.ibm.com/docs/databases-for-mysql?topic=databases-for-mysql-managing-mysql-connections&format=markdown){: .external}.

## How to calculate the MySQL `max_connections` variable
{: #changing-configuration-calculate-max-connections}

`max_connections` is a configuration parameter in MySQL that determines the maximum number of concurrent connections that can be established with the database server.

### MySQL `max_connections` basic formula
{: #changing-configuration-calculate-max-connections-formula}

The basic formula for calculating `max_connections` is:

```text
Available RAM = Global Buffers + (Thread Buffers x `max_connections`)
```

To retrieve a list of buffers and their values, use a command like:

```sh
SHOW VARIABLES LIKE '%buffer%';
```
{: pre}

## Using the Cloud Databases CLI plug-in
{: #using-cli}

Check the default configuration of your deployment by using a command like:

```sh
ibmcloud cdb deployment-configuration-schema <deployment name or CRN>
```
This command only returns the default configuration. Changes to the default configuration are not shown.
{: note}

{: pre}

To change your configuration through the Cloud Databases CLI-plugin, use `deployment-configuration` command:

```sh
ibmcloud cdb deployment-configuration <deployment name or CRN> [@JSON_FILE | JSON_STRING]
```
{: pre}

The command reads the changes that you would like to make from the JSON object or a file. For more information, see the [CLI reference page](https://cloud.ibm.com/docs/databases-cli-plugin?topic=databases-cli-plugin-cdb-reference&format=markdown#deployment-configuration).

## Using the Cloud Databases API
{: #using-api}

There are two deployment-configuration endpoints, one for viewing the configuration schema and one for changing the configuration. To view the configuration schema, send a `GET` request to `/deployments/{id}/configuration/schema`.

To change the configuration, send the settings that you would like to change as a JSON object in the request body of a `PATCH` request to `/deployments/{id}/configuration`.

For more information, see [API Reference](https://cloud.ibm.com/apidocs/cloud-databases-api#change-your-database-configuration){: external}.

## Databases for MySQL time zone settings
{: #mem-settings}

The time zone for Databases for MySQL deployments is always Coordinated Universal Time. Configure your time zone with the Cloud Databases API or the CLI change your time zone to a named time zone (recommended) or an offset of a time zone.

You are required to configure the time zone again on both restored instances and read-replicas. Although the time zone tables are restored (in the case of a restore) and replicated (in the case of a read-replica), the `@@global.time_zone` value is not. To set this value, use the same API calls as before, but with the new CRNs.
{: note}

### Configuring your Databases for MySQL time zone settings
{: #mem-settings-config}

At provisioning, a Cloud Databases deployment is configured to Coordinated Universal Time. Reconfiguring your time zone is a persistent change, which must be undertaken for each of your Cloud Databases deployments.

Configuring your time zone sets the global time zone within your MySQL instance. In the instance that a failover occurs, your time zone setting is propagated as part of replication, as the time zone setting is written to the MySQL config file. The exception to this is if you restore an instance to a point in time before you configured your preferred time zone.

If you configure your time zone to one that features Daylight Saving Time, adjustments are part of the configuration. No action is necessary on your part.
Using a specific time zone is better than using an offset time.

Cloud Databases validates the `time_zone` parameter value. If you configure your deployment with an invalid value, the configuration fails. The valid named `time_zone values` can be found [here](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones){: external}.
{: note}

### Changing the time zone in the Cloud Databases API
{: #change-time-zone-api}
{: api}

Example offset:

```sh
curl -v -XPATCH -H "Authorization: Bearer $token" -H "Content-Type: application/json" https://api.<region>.databases.cloud.ibm.com/v5/ibm/deployments/<crn>/configuration -d '{"configuration": {"time_zone": "<EXAMPLE OFFSET"}}'
```
{: pre}

Example named time zone:
```sh
curl -v -XPATCH -H "Authorization: Bearer $token" -H "Content-Type: application/json" https://api.<region>.databases.cloud.ibm.com/v5/ibm/deployments/<crn>/configuration -d '{"configuration": {"time_zone": "<EXAMPLE TIME ZONE"}}'
```
{: pre}

### Changing the time zone in the Cloud Databases CLI
{: #change-time-zone-cli}
{: cli}

Example named time zone
```sh
ibmcloud cdb deployment-configuration <crn> '{"time_zone": "US/Pacific"}'
```
{: pre}

## Available Databases for MySQL configuration settings
{: #available-config-settings}

[`innodb_buffer_pool_size_percentage`](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_buffer_pool_size){: .external}

- Description: The percentage of memory to use for `innodb_buffer_pool_size`. The default value of 50% is a conservative value and works for databases of any size. If your database requires more RAM, this value can be increased. Setting this value too high can exceed your database's memory limits, which can cause it to crash.
- Default: `50`
- Minimum: `10`
- Maximum: `100`
- Restarts database? - `true`

[`innodb_log_buffer_size`](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_log_buffer_size){: .external}

- Description: The size in bytes of the buffer that InnoDB uses to write to the [log files](https://dev.mysql.com/doc/refman/8.0/en/glossary.html#glos_log_file){: .external} on disk.
- Default: `33554432`
- Minimum: `1048576`
- Maximum: `4294967295`
- Restarts database? - `true`

[`innodb_log_file_size`](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_log_file_size){: .external}

- Description: The size in bytes of each [log file](https://dev.mysql.com/doc/refman/8.0/en/glossary.html#glos_log_file){: .external} in a [log group](https://dev.mysql.com/doc/refman/8.0/en/glossary.html#glos_log_group){: .external}. `Innodb_log_file_size` and `innodb_log_files_in_group` have been superseded by `innodb_redo_log_capacity`. Setting `innodb_log_file_size` will also set `innodb_redo_log_capacity`.
- Default: `2147483648`
- Minimum: `4194304`
- Maximum: `274877906900`
- Restarts database? - `false`

[`innodb_lru_scan_depth`](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_lru_scan_depth){: .external}

- Description: A parameter that influences the algorithms and heuristics for the [flush](https://dev.mysql.com/doc/refman/8.0/en/glossary.html#glos_flush){: .external} operation for the InnoDB [buffer pool](https://dev.mysql.com/doc/refman/8.0/en/glossary.html#glos_buffer_pool){: .external}. A setting smaller than the default is generally suitable for most workloads. A value that is much higher than necessary might impact performance. Consider increasing the value only if you have spare I/O capacity under a typical workload.
- Default: `256`
- Minimum: `128`
- Maximum: `2048`
- Restarts database? - `false`

[`innodb_write_io_threads`](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_write_io_threads){: .external}

- Description: The number of I/O threads for write operations in InnoDB.
- Default: `4`
- Minimum: `1`
- Maximum: `64`
- Restarts database? - `true`

[`max_allowed_packet`](https://dev.mysql.com/doc/refman/8.0/en/packet-too-large.html){: .external}

- Default - `1073741824`
- Minimum - `1024`
- Maximum - `1073741824`
- Restarts database? - `false`

[`max_prepared_stmt_count`](https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_max_prepared_stmt_count)

- Description - Specifies the total number of prepared statements on the server.
- Default - `16382`
- Minimum - `0`
- Maximum - (version ≤ 8.0.17) `1048576`, (version ≥ 8.0.18) `4194304`
- Restarts database? - `false`

[`max_connections`](https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_max_connections){: .external}

- Default - `200`
- Restarts database? - `false`

 You might need to [scale before you increase max connections](https://cloud.ibm.com/docs/databases-for-mysql?topic=databases-for-mysql-mysql-ha-dr&format=markdown#connection-limits-ha).{: note}

[`mysql_max_binlog_age_sec`](https://dev.mysql.com/doc/refman/8.0/en/replication-options-binary-log.html){: .external}

- Default - `1800`
- Restarts database? - `false`

[`net_write_timeout`](https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_net_write_timeout){: .external}

- Description: The number of seconds to wait for a block to be written to a connection before aborting the write.
- Default: `60`
- Minimum: `1`
- Maximum: `7200`
- Restarts database? - `false`

[`sql_mode`](https://dev.mysql.com/doc/refman/8.0/en/sql-mode.html){: .external}

- Allowable values:
   - `ALLOW_INVALID_DATES`
   - `ANSI_QUOTES`
   - `ERROR_FOR_DIVISION_BY_ZERO`
   - `HIGH_NOT_PRECEDENCE`
   - `IGNORE_SPACE`
   - `NO_AUTO_CREATE_USER`
   - `NO_AUTO_VALUE_ON_ZERO`
   - `NO_BACKSLASH_ESCAPES`
   - `NO_DIR_IN_CREATE`
   - `NO_ENGINE_SUBSTITUTION`
   - `NO_FIELD_OPTIONS`
   - `NO_KEY_OPTIONS`
   - `NO_TABLE_OPTIONS`
   - `NO_UNSIGNED_SUBTRACTION`
   - `NO_ZERO_DATE`
   - `NO_ZERO_IN_DATE`
   - `ONLY_FULL_GROUP_BY`
   - `PAD_CHAR_TO_FULL_LENGTH`
   - `PIPES_AS_CONCAT`
   - `REAL_AS_FLOAT`
   - `STRICT_ALL_TABLES`
   - `STRICT_TRANS_TABLES`
- Restarts database? - `false`

[`time_zone`](https://dev.mysql.com/doc/refman/8.0/en/time-zone-support.html#time-zone-variables){: .external}

- Description: The time zone that is currently set on the server is '+00:00' (Coordinated Universal Time) by default. However, it can also be set to a specific offset from Coordinated Universal Time in the format of [H]H:MM, with a + or - prefix, for example '+10:00', '-6:00', or '+05:30'. Named time zones like 'MET' or 'US/Pacific' can also be used.
- Default: `+00:00`
- Type: `string`
- Restarts database? - `false`

[`wait_timeout`](https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_wait_timeout){: .external}

- Description: The number of seconds the server waits for activity on a noninteractive connection before closing it.
- Default: `28800`
- Minimum: `1`
- Maximum: `31536000`
- Restarts database? - `false`

[`innodb_read_io_threads`](https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_read_io_threads){: .external}

- Description: The number of I/O threads for read operations in InnoDB.
- Default: `4`
- Minimum: `1`
- Maximum: `64`
- Restarts database? - `true`

[`net_read_timeout`](https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_net_read_timeout){: .external}

- Description: The number of seconds to wait for more data from a connection before aborting the read.
- Default: `30`
- Minimum: `1`
- Maximum: `7200`
- Restarts database? - `false`