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--- title: How to configure Azure Cache for Redis description: Understand the default Redis configuration for Azure Cache for Redis and learn how to configure your Azure Cache for Redis instances. ms.topic: conceptual ms.date: 05/07/2024 appliesto: - ✅ Azure Cache for Redis ms.custom: engagement-fy23 --- # How to configure Azure Cache for Redis [!INCLUDE [cache-retirement-alert](includes/cache-retirement-alert.md)] This article describes the configurations available for your Azure Cache for Redis instances. This article also covers the [default Redis server configuration](#default-redis-server-configuration) for Azure Cache for Redis instances. > [!NOTE] > For more information on configuring and using premium cache features, see [How to configure persistence](cache-how-to-premium-persistence.md) and [How to configure Virtual Network support](cache-how-to-premium-vnet.md). > ## Configure Azure Cache for Redis settings [!INCLUDE [redis-cache-create](~/reusable-content/ce-skilling/azure/includes/azure-cache-for-redis/includes/redis-cache-create.md)] You can view and configure the following settings using the **Resource Menu**. The settings that you see depend on the tier of your cache. For example, you don't see **Reboot** when using the Enterprise tier. - [Overview](#overview) - [Activity log](#activity-log) - [Access control (IAM)](#access-control-iam) - [Tags](#tags) - [Diagnose and solve problems](#diagnose-and-solve-problems) - [Events](#events) - [Settings](#settings) - [Authentication](#authentication) - [Advanced settings](#advanced-settings) - [Scale](#scale) - [Cluster size](#cluster-size) - [Data persistence](#data-persistence) - [Identity](#identity) - [Schedule updates](#schedule-updates) - [Geo-replication](#geo-replication) - [Virtual Network](#virtual-network) - [Private Endpoint](#private-endpoint) - [Firewall](#firewall) - [Properties](#properties) - [Locks](#locks) - Administration - [Import data](#importexport) - [Export data](#importexport) - [Reboot](#reboot) - [Monitoring](#monitoring) - Automation - [Tasks (preview)](#tasks) - [Export template](#export-template) - Support & troubleshooting settings - [Resource health](#resource-health) - [New support request](#new-support-request) ## Overview The **Overview** section provides you with basic information about your cache, such as name, ports, pricing tier, and selected cache metrics. ### Activity log Select **Activity log** to view actions done to your cache. You can also use filtering to expand this view to include other resources. For more information on working with audit logs, see [Audit operations with Resource Manager](/azure/azure-monitor/essentials/activity-log). For more information on monitoring the activity log, see [Activity log](../redis/monitor-cache.md#azure-activity-log). ### Access control (IAM) The **Access control (IAM)** section provides support for Azure role-based access control (Azure RBAC) in the Azure portal. This configuration helps organizations meet their access management requirements simply and precisely. For more information, see [Azure role-based access control in the Azure portal](/azure/role-based-access-control/role-assignments-portal). ### Tags The **Tags** section helps you organize your resources. For more information, see [Using tags to organize your Azure resources](/azure/azure-resource-manager/management/tag-resources). ### Diagnose and solve problems Select **Diagnose and solve problems** to be provided with common issues and strategies for resolving them. ### Events Select **Events** to add event subscriptions to your cache. Use events to build reactive, event-driven apps with the fully managed event routing service that is built into Azure. The Event Grid helps you build automation into your cloud infrastructure, create serverless apps, and integrate across services and clouds. For more information, see [What is Azure Event Grid](/azure/event-grid/overview). ## Redis console You can securely issue commands to your Azure Cache for Redis instances using the **Redis Console**, which is available in the Azure portal for Basic, Standard and Premium cache tiers. > [!IMPORTANT] > The Redis Console doesn't work when a cache has any of the following: > > - [Virtual Network](cache-how-to-premium-vnet.md). When your cache is part of a VNet, only clients in the VNet can access the cache. Because Redis Console runs in your local browser, which is outside the VNet, it can't connect to your cache. > - [Private Link](cache-private-link.md) > - [Access Keys disabled](cache-azure-active-directory-for-authentication.md#disable-access-key-authentication-on-your-cache) > > [!NOTE] > > To access Redis Console, you would need at least **Contributor** built-in role. > To access the Redis Console, select **Console** tab in the working pane of Resource menu. :::image type="content" source="media/cache-configure/redis-console-menu.png" alt-text="Screenshot that highlights the Console button."::: To issue commands against your cache instance, type the command you want into the console. :::image type="content" source="media/cache-configure/redis-console.png" alt-text="Screenshot that shows the Redis Console with the input command and results."::: > [!NOTE] > > Not all Redis commands are supported in Azure Cache for Redis. For a list of Redis commands that are disabled for Azure Cache for Redis, see [Redis commands not supported in Azure Cache for Redis](#redis-commands-not-supported-in-azure-cache-for-redis) section. > For more information about Redis commands, see [https://redis.io/commands](https://redis.io/commands). > ### Using the Redis Console with a premium clustered cache When using the Redis Console with a premium clustered cache, you can issue commands to a single shard of the cache. To issue a command to a specific shard, first connect to the shard you want by selecting it on the shard picker. :::image type="content" source="media/cache-configure/redis-console-premium-cluster.png" alt-text="Redis console"::: If you attempt to access a key that is stored in a different shard than the connected shard, you receive an error message similar to the following message: ```azurecli-interactive shard1>get myKey (error) MOVED 866 13.90.202.154:13000 (shard 0) shard1>get myKey (error) MOVED 866 13.90.202.154:13000 (shard 0) ``` In the previous example, shard 1 is the selected shard, but `myKey` is located in shard 0, as indicated by the `(shard 0)` portion of the error message. In this example, to access `myKey`, select shard 0 using the shard picker, and then issue the desired command. ## Move your cache to a new subscription You can move your cache to a new subscription by selecting **Move**. :::image type="content" source="media/cache-configure/redis-cache-move.png" alt-text="Move Azure Cache for Redis"::: For information on moving resources from one resource group to another, and from one subscription to another, see [Move resources to new resource group or subscription](/azure/azure-resource-manager/management/move-resource-group-and-subscription). ## Settings The **Settings** section allows you to access and configure the following settings for your cache. - [Authentication](#authentication) - [Advanced settings](#advanced-settings) - [Scale](#scale) - [Cluster size](#cluster-size) - [Data persistence](#data-persistence) - [Schedule updates](#schedule-updates) - [Geo-replication](#geo-replication) - [Private endpoint](#private-endpoint) - [Virtual Network](#virtual-network) - [Firewall](#firewall) - [Properties](#properties) - [Locks](#locks) ### Authentication You have two options for authentication: access keys and Microsoft Entra Authentication. #### [Access keys](#tab/access-keys) Select **Access keys** to view or regenerate the access keys for your cache. These keys are used by the clients connecting to your cache. :::image type="content" source="media/cache-configure/redis-cache-manage-keys.png" alt-text="Screenshot showing Authentication selected in the Resource menu and access Keys in the working pane."::: #### [Microsoft Entra Authentication](#tab/entra) Select **Microsoft Entra Authentication** to a password-free authentication mechanism by integrating with Microsoft Entra ID. This integration also includes role-based access control functionality provided through access control lists (ACLs) supported in open source Redis. :::image type="content" source="media/cache-configure/cache-microsoft-entra.png" alt-text="Screenshot showing Authentication selected in the Resource menu and Microsoft Entra ID in the working pane."::: --- ### Advanced settings The following settings are configured on the **Advanced settings** on the left. - [Access Ports](#access-ports) - [Memory policies](#memory-policies) - [Keyspace notifications (advanced settings)](#keyspace-notifications-advanced-settings) #### Access Ports By default, non-TLS/SSL access is disabled for new caches. To enable the non-TLS port, Select **No** for **Allow access only via SSL** on the **Advanced settings** on the left and then Select **Save**. > [!NOTE] > TLS access to Azure Cache for Redis supports TLS 1.0, 1.1 and 1.2 currently, but versions 1.0 and 1.1 are being retired soon. Please read our [Remove TLS 1.0 and 1.1 page](cache-remove-tls-10-11.md) for more details. :::image type="content" source="media/cache-configure/redis-cache-access-ports.png" alt-text="Azure Cache for Redis Access Ports"::: #### Memory policies Use the **Maxmemory policy**, **maxmemory-reserved**, and **maxfragmentationmemory-reserved** settings from **Advanced settings** from the Resource menu on the left to configure the memory policies for the cache. When you create a cache, the values `maxmemory-reserved` and `maxfragmentationmemory-reserved` default to 10% of `maxmemory`, which is the cache size. :::image type="content" source="media/cache-configure/redis-cache-maxmemory-policy.png" alt-text="Azure Cache for Redis Maxmemory Policy"::: **Maxmemory policy** configures the eviction policy for the cache and allows you to choose from the following eviction policies: - `volatile-lru`: The default eviction policy. It removes the least recently used key out of all the keys with an expiration set. - `allkeys-lru`: Removes the least recently used key. - `volatile-random`: Removes a random key that has an expiration set. - `allkeys-random`: Removes a random key. - `volatile-ttl`: Removes the key with the shortest time to live based on the expiration set for it. - `noeviction`: No eviction policy. Returns an error message if you attempt to insert data. - `volatile-lfu`: Evicts the least frequently used keys out of all keys with an expire field set. - `allkeys-lfu`: Evicts the least frequently used keys out of all keys. For more information about `maxmemory` policies, see [Eviction policies](https://redis.io/topics/lru-cache#eviction-policies). The **maxmemory-reserved** setting configures the amount of memory in MB per instance in a cluster that is reserved for noncache operations, such as replication during failover. Setting this value allows you to have a more consistent Redis server experience when your load varies. This value should be set higher for workloads that write large amounts of data. When memory is reserved for such operations, it's unavailable for storage of cached data. The minimum and maximum values on the slider are 10% and 60%, shown in megabytes. You must set the value in that range. The **maxfragmentationmemory-reserved** setting configures the amount of memory in MB per instance in a cluster that is reserved to accommodate for memory fragmentation. When you set this value, the Redis server experience is more consistent when the cache is full or close to full and the fragmentation ratio is high. When memory is reserved for such operations, it's unavailable for storage of cached data. The minimum and maximum values on the slider are 10% and 60%, shown in megabytes. You must set the value in that range. When choosing a new memory reservation value (**maxmemory-reserved** or **maxfragmentationmemory-reserved**), consider how this change might affect a cache that is already running with large amounts of data in it. For instance, if you have a 53-GB cache with 49 GB of data, then change the reservation value to 8 GB, this change drops the max available memory for the system down to 45 GB. If either your current `used_memory` or your `used_memory_rss` values are higher than the new limit of 45 GB, then the system has to evict data until both `used_memory` and `used_memory_rss` are below 45 GB. Eviction can increase server load and memory fragmentation. For more information on cache metrics such as `used_memory` and `used_memory_rss`, see [Create your own metrics](../redis/monitor-cache.md#create-your-own-metrics). > [!IMPORTANT] > The **maxmemory-reserved** and **maxfragmentationmemory-reserved** settings are available for Basic,Standard and Premium caches. > #### Keyspace notifications (advanced settings) Redis keyspace notifications are configured on the **Advanced settings** on the left. Keyspace notifications allow clients to receive notifications when certain events occur. :::image type="content" source="media/cache-configure/redis-cache-advanced-settings.png" alt-text="Azure Cache for Redis Advanced Settings":::) > [!IMPORTANT] > Keyspace notifications and the **notify-keyspace-events** setting are only available for Standard and Premium caches. > For more information, see [Redis Keyspace Notifications](https://redis.io/topics/notifications). For sample code, see the [KeySpaceNotifications.cs](https://github.com/rustd/RedisSamples/blob/master/HelloWorld/KeySpaceNotifications.cs) file in the [Hello world](https://github.com/rustd/RedisSamples/tree/master/HelloWorld) sample. ### Scale Select **Scale** to view or change the pricing tier for your cache. For more information on scaling, see [How to Scale Azure Cache for Redis](cache-how-to-scale.md). :::image type="content" source="media/cache-configure/pricing-tier.png" alt-text="Azure Cache for Redis pricing tier"::: ### Cluster Size Select **Cluster Size** to change the cluster size for a running premium cache with clustering enabled. :::image type="content" source="media/cache-configure/redis-cache-redis-cluster-size.png" alt-text="Cluster size"::: To change the cluster size, use the slider or type a number between 1 and 10 in the **Shard count** text box. Then, select **OK** to save. ### Data persistence Select **Data persistence** to enable, disable, or configure data persistence for your premium cache. Azure Cache for Redis offers Redis persistence using either RDB persistence or AOF persistence. For more information, see [How to configure persistence for a Premium Azure Cache for Redis](cache-how-to-premium-persistence.md). > [!IMPORTANT] > Redis data persistence is for Premium caches, Enterprise caches (Preview), and Enterprise Flash caches (Preview). ### Identity Use **Identity** to configure managed identities. Managed identities are a common tool used in Azure to help developers minimize the burden of managing secrets and sign-in information. Presently, you can only use managed identities for storage. For more information, see [Managed identity for storage](cache-managed-identity.md). > [!NOTE] > Managed identity functionality is only available in the Premium tier for use with storage. ### Schedule updates The **Schedule updates** section allows you to choose a maintenance window for Redis server updates for your cache. > [!IMPORTANT] > The maintenance window applies only to Redis server updates, and not to any Azure updates or updates to the operating system of the VMs that host the cache. :::image type="content" source="media/cache-configure/redis-schedule-updates.png" alt-text="Schedule updates"::: To specify a maintenance window, check the days you want. Then, specify the maintenance window start hour for each day, and select **OK**. The maintenance window time is in UTC. For more information and instructions, see [Update channel and Schedule updates](cache-administration.md#update-channel-and-schedule-updates). ### Geo-replication **Geo-replication**, on the Resource menu, provides a mechanism for linking two Premium tier Azure Cache for Redis instances. One cache is named as the primary linked cache, and the other as the secondary linked cache. The secondary linked cache becomes read-only, and data written to the primary cache is replicated to the secondary linked cache. This functionality can be used to replicate a cache across Azure regions. > [!IMPORTANT] > **Geo-replication** is only available for Premium tier caches. For more information and instructions, see [How to configure Geo-replication for Azure Cache for Redis](cache-how-to-geo-replication.md). ### Virtual Network The **Virtual Network** section allows you to configure the virtual network settings for your cache. Virtual networks are limited to Premium caches. For information on creating a premium cache with VNET support and updating its settings, see [How to configure Virtual Network Support for a Premium Azure Cache for Redis](cache-how-to-premium-vnet.md). > [!IMPORTANT] > Virtual network settings are only available for premium caches that were configured with VNet support during cache creation. ### Private endpoint The **Private Endpoint** section allows you to configure the private endpoint settings for your cache. Private endpoint is supported on all cache tiers Basic, Standard, Premium, and Enterprise. We recommend using private endpoint instead of VNets. Private endpoints are easy to set up or remove, are supported on all tiers, and can connect your cache to multiple different VNets at once. For more information, see [Azure Cache for Redis with Azure Private Link](cache-private-link.md). ### Firewall - Firewall rules configuration is available for all Basic, Standard, and Premium tiers. - Firewall rules configuration isn't available for Enterprise nor Enterprise Flash tiers. Select **Firewall** to view and configure firewall rules for cache. :::image type="content" source="media/cache-configure/redis-firewall-rules.png" alt-text="Firewall"::: You can specify firewall rules with a start and end IP address range. When firewall rules are configured, only client connections from the specified IP address ranges can connect to the cache. When a firewall rule is saved, there's a short delay before the rule is effective. This delay is typically less than one minute. > [!IMPORTANT] > Connections from Azure Cache for Redis monitoring systems are always permitted, even if firewall rules are configured. ### Properties Select **Properties** to view information about your cache, including the cache endpoint and ports. :::image type="content" source="media/cache-configure/redis-cache-properties.png" alt-text="Azure Cache for Redis Properties"::: ### Locks The **Locks** section allows you to lock a subscription, resource group, or resource to prevent other users in your organization from accidentally deleting or modifying critical resources. For more information, see [Lock resources with Azure Resource Manager](/azure/azure-resource-manager/management/lock-resources). ## Administration settings The settings in the **Administration** section allow you to perform the following administrative tasks for your cache. :::image type="content" source="media/cache-configure/redis-cache-administration.png" alt-text="Administration"::: - [Import data](#importexport) - [Export data](#importexport) - [Reboot](#reboot) ### Import/Export Import/Export is an Azure Cache for Redis data management operation that allows you to import and export data in the cache. You can import and export an Azure Cache for Redis Database (RDB) snapshot from a premium cache to a page blob in an Azure Storage Account. Use Import/Export to migrate between different Azure Cache for Redis instances or populate the cache with data before use. You can use import with Redis-compatible RDB files from any Redis server running in any cloud or environment: - including Redis running on Linux - Windows - any cloud provider such as Amazon Web Services and others Importing data is an easy way to create a cache with prepopulated data. During the import process, Azure Cache for Redis loads the RDB files from Azure storage into memory, and then inserts the keys into the cache. Export allows you to export the data stored in Azure Cache for Redis to Redis compatible RDB files. You can use this feature to move data from one Azure Cache for Redis instance to another or to another Redis server. During the export process, a temporary file is created on the VM that hosts the Azure Cache for Redis server instance. The temporary file is uploaded to the designated storage account. When the export operation completes with either a status of success or failure, the temporary file is deleted. > [!IMPORTANT] > Import/Export is only available for Premium tier caches. For more information and instructions, see [Import and Export data in Azure Cache for Redis](cache-how-to-import-export-data.md). > ### Reboot The **Reboot** item allows you to reboot the nodes of your cache. This reboot capability enables you to test your application for resiliency if there's a failure of a cache node. :::image type="content" source="media/cache-configure/redis-cache-reboot.png" alt-text="Reboot"::: If you have a premium cache with clustering enabled, you can select which shards of the cache to reboot. :::image type="content" source="media/cache-configure/redis-cache-reboot-cluster.png" alt-text="Screenshot that shows where to select which shards of the cache to reboot."::: To reboot one or more nodes of your cache, select the desired nodes and select **Reboot**. If you have a premium cache with clustering enabled, select the shards to reboot, and then select **Reboot**. After a few minutes, the selected node(s) reboot, and are back online a few minutes later. > [!IMPORTANT] > Reboot is not yet available for the Enterprise tier. Reboot is available for all other tiers. For more information and instructions, see [Azure Cache for Redis administration - Reboot](cache-administration.md#reboot). > ## Monitoring The **Monitoring** section allows you to configure diagnostics and monitoring for your Azure Cache for Redis instance. - For more information on Azure Cache for Redis monitoring and diagnostics, see [Monitor Azure Cache for Redis](../redis/monitor-cache.md). - For information on how to set up and use Azure Cache for Redis monitoring and diagnostics, see [Monitor Azure Cache for Redis](../redis/monitor-cache.md). :::image type="content" source="media/cache-configure/redis-cache-diagnostics.png" alt-text="Diagnostics"::: ### Insights Use **Insights** to see groups of predefined tiles and charts to use as starting point for your cache metrics. For more information, see [Insights](../redis/monitor-cache.md#insights). ### Metrics Select **Metrics** to create your own custom chart to track the metrics you want to see for your cache. For more information, see [Create your own metrics](../redis/monitor-cache.md#create-your-own-metrics). ### Alerts Select **Alerts** to configure alerts based on Azure Cache for Redis metrics. For more information, see [Create alerts](../redis/monitor-cache.md#create-alerts). ### Diagnostic settings By default, cache metrics in Azure Monitor are [stored for 30 days](/azure/azure-monitor/essentials/data-platform-metrics) and then deleted. To persist your cache metrics for longer than 30 days, select **Diagnostics settings** to [configure the storage account](../redis/monitor-cache.md#data-storage) used to store cache diagnostics. >[!NOTE] >In addition to archiving your cache metrics to storage, you can also [stream them to an Event hub or send them to Azure Monitor logs](/azure/azure-monitor/essentials/stream-monitoring-data-event-hubs). ### Advisor recommendations The **Advisor recommendations** displays recommendations for your cache. During normal operations, no recommendations are displayed. :::image type="content" source="media/cache-configure/redis-cache-no-recommendations.png" alt-text="Screenshot that shows where the Advisor recommendations are displayed but there are no current ones."::: If any conditions occur during the operations of your cache such as imminent changes, high memory usage, network bandwidth, or server load, an alert is displayed in the **Overview** of the Resource menu. :::image type="content" source="media/cache-configure/redis-cache-recommendations-alert.png" alt-text="Screenshot that shows where alerts are displayed in when Overview is selected in the Resource menu."::: Further information can be found on the **Recommendations** in the working pane of the Azure portal. :::image type="content" source="media/cache-configure/redis-cache-recommendations.png" alt-text="Screenshot that shows Advisor recommendations"::: You can monitor these metrics on the [Monitoring](../redis/monitor-cache.md) section of the Resource menu. | Azure Cache for Redis metric | More information | | --- | --- | | Network bandwidth usage |[Cache performance - available bandwidth](./cache-planning-faq.yml#azure-cache-for-redis-performance) | | Connected clients |[Default Redis server configuration - max clients](#maxclients) | | Server load |[Redis Server Load](../redis/monitor-cache.md#view-cache-metrics) | | Memory usage |[Cache performance - size](./cache-planning-faq.yml#azure-cache-for-redis-performance) | To upgrade your cache, select **Upgrade now** to change the pricing tier and [scale](#scale) your cache. For more information on choosing a pricing tier, see [Choosing the right tier](cache-overview.md#choosing-the-right-tier). ### Workbooks Organize your metrics into groups so that you display metric information in a coherent and effective way. ## Automation Azure Automation delivers a cloud-based automation, operating system updates, and configuration service that supports consistent management across your Azure and non-Azure environments. ### Tasks Select **Tasks** to help you manage Azure Cache for Redis resources more easily. These tasks vary in number and availability, based on the resource type. Presently, you can only use the **Send monthly cost for resource** template to create a task while in preview. For more information, see [Manage Azure resources and monitor costs by creating automation tasks](/azure/logic-apps/create-automation-tasks-azure-resources). ### Export template Select **Export template** to build and export a template of your deployed resources for future deployments. For more information about working with templates, see [Deploy resources with Azure Resource Manager templates](/azure/azure-resource-manager/templates/deploy-powershell). ## Support & troubleshooting settings The settings in the **Support + troubleshooting** section provide you with options for resolving issues with your cache. :::image type="content" source="media/cache-configure/redis-cache-support-troubleshooting.png" alt-text="Support and troubleshooting"::: - [Resource health](#resource-health) - [New support request](#new-support-request) ### Resource health **Resource health** watches your resource and tells you if it's running as expected. For more information about the Azure Resource health service, see [Azure Resource health overview](/azure/service-health/resource-health-overview). > [!NOTE] > Resource health is currently unable to report on the health of Azure Cache for Redis instances hosted in a virtual network. For more information, see [Do all cache features work when hosting a cache in a VNET?](cache-how-to-premium-vnet.md#do-all-cache-features-work-when-a-cache-is-hosted-in-a-virtual-network) ### New support request Select **New support request** to open a support request for your cache. ## Default Redis server configuration New Azure Cache for Redis instances are configured with the following default Redis configuration values: > [!NOTE] > The settings in this section cannot be changed using the `StackExchange.Redis.IServer.ConfigSet` method. If this method is called with one of the commands in this section, an exception similar to the following example is thrown: > > `StackExchange.Redis.RedisServerException: ERR unknown command 'CONFIG'` > > Any values that are configurable, such as **max-memory-policy**, are configurable through the Azure portal or command-line management tools such as Azure CLI or PowerShell. | Setting | Default value | Description | | --- | --- | --- | | `databases` |16 |The default number of databases is 16 but you can configure a different number based on the pricing tier.¹ The default database is DB 0, you can select a different one on a per-connection basis using `connection.GetDatabase(dbid)` where `dbid` is a number between `0` and `databases - 1`. | | `maxclients` |Depends on the pricing tier² |This value is the maximum number of connected clients allowed at the same time. Once the limit is reached Redis closes all the new connections, returning a 'max number of clients reached' error. | | `maxmemory-reserved` | 10% of `maxmemory` | The allowed range for `maxmemory-reserved` is 10% - 60% of `maxmemory`. If you try to set these values lower than 10% or higher than 60%, they're reevaluated and set to the 10% minimum and 60% maximum. The values are rendered in megabytes. | | `maxfragmentationmemory-reserved` | 10% of `maxmemory` | The allowed range for `maxfragmentationmemory-reserved` is 10% - 60% of `maxmemory`. If you try to set these values lower than 10% or higher than 60%, they're reevaluated and set to the 10% minimum and 60% maximum. The values are rendered in megabytes. | | `maxmemory-policy` |`volatile-lru` | Maxmemory policy is the setting used by the Redis server to select what to remove when `maxmemory` (the size of the cache that you selected when you created the cache) is reached. With Azure Cache for Redis, the default setting is `volatile-lru`. This setting removes the keys with an expiration set using an LRU algorithm. This setting can be configured in the Azure portal. For more information, see [Memory policies](#memory-policies). | | `maxmemory-samples` |3 |To save memory, LRU and minimal TTL algorithms are approximated algorithms instead of precise algorithms. By default Redis checks three keys and picks the one that was used less recently. | | `lua-time-limit` |5,000 |Max execution time of a Lua script in milliseconds. If the maximum execution time is reached, Redis logs that a script is still in execution after the maximum allowed time, and starts to reply to queries with an error. | | `lua-event-limit` |500 |Max size of script event queue. | | `client-output-buffer-limit normal` / `client-output-buffer-limit pubsub` |`0 0 0` / `32mb 8mb 60` |The client output buffer limits can be used to force disconnection of clients that aren't reading data from the server fast enough for some reason. A common reason is that a Pub/Sub client can't consume messages as fast as the publisher can produce them. For more information, see [https://redis.io/topics/clients](https://redis.io/topics/clients). | ### Databases ¹The limit for `databases` is different for each Azure Cache for Redis pricing tier and can be set at cache creation. If no `databases` setting is specified during cache creation, the default is 16. - Basic and Standard caches - C0 (250 MB) cache - up to 16 databases - C1 (1 GB) cache - up to 16 databases - C2 (2.5 GB) cache - up to 16 databases - C3 (6 GB) cache - up to 16 databases - C4 (13 GB) cache - up to 32 databases - C5 (26 GB) cache - up to 48 databases - C6 (53 GB) cache - up to 64 databases - Premium caches - P1 (6 GB - 60 GB) - up to 16 databases - P2 (13 GB - 130 GB) - up to 32 databases - P3 (26 GB - 260 GB) - up to 48 databases - P4 (53 GB - 530 GB) - up to 64 databases - P5 (120 GB - 1200 GB) - up to 64 databases - All premium caches with Redis cluster enabled - Redis cluster only supports use of database 0 so the `databases` limit for any premium cache with Redis cluster enabled is effectively 1 and the [Select](https://redis.io/commands/select) command isn't allowed. For more information about databases, see [What are Redis databases?](cache-development-faq.yml#what-are-redis-databases-) > [!NOTE] > The `databases` setting can be configured only during cache creation and only using PowerShell, CLI, or other management clients. For an example of configuring `databases` during cache creation using PowerShell, see [New-AzRedisCache](../redis/how-to-manage-redis-cache-powershell.md#databases). > ### Maxclients ²The `maxclients` property is different for each Azure Cache for Redis pricing tier. - Basic and Standard caches - C0 (250 MB) cache - up to 256 connections - C1 (1 GB) cache - up to 1,000 connections - C2 (2.5 GB) cache - up to 2,000 connections - C3 (6 GB) cache - up to 5,000 connections - C4 (13 GB) cache - up to 10,000 connections - C5 (26 GB) cache - up to 15,000 connections - C6 (53 GB) cache - up to 20,000 connections - Premium caches - P1 (6 GB - 60 GB) - up to 7,500 connections - P2 (13 GB - 130 GB) - up to 15,000 connections - P3 (26 GB - 260 GB) - up to 30,000 connections - P4 (53 GB - 530 GB) - up to 40,000 connections - P5: (120 GB - 1200 GB) - up to 40,000 connections > [!NOTE] > While each size of cache allows *up to* a certain number of connections, each connection to Redis has overhead associated with it. An example of such overhead would be CPU and memory usage as a result of TLS/SSL encryption. The maximum connection limit for a given cache size assumes a lightly loaded cache. If load from connection overhead *plus* load from client operations exceeds capacity for the system, the cache can experience capacity issues even if you have not exceeded the connection limit for the current cache size. > ## Redis commands not supported in Azure Cache for Redis Configuration and management of Azure Cache for Redis instances is managed by Microsoft, which disables the following commands. If you try to invoke them, you receive an error message similar to `"(error) ERR unknown command"`. - ACL - BGREWRITEAOF - BGSAVE - CLUSTER - Cluster write commands are disabled, but read-only cluster commands are permitted. - CONFIG - DEBUG - MIGRATE - PSYNC - REPLICAOF - REPLCONF - Azure cache for Redis instances don't allow customers to add external replicas. This [command](https://redis.io/commands/replconf/) is normally only sent by servers. - SAVE - SHUTDOWN - SLAVEOF - SYNC For cache instances using active geo-replication, the following commands are also blocked to prevent accidental data loss: - FLUSHALL - FLUSHDB > [!IMPORTANT] > Because configuration and management of Azure Cache for Redis instances is managed by Microsoft, some commands are disabled. The commands are listed above. If you try to invoke them, you receive an error message similar to `"(error) ERR unknown command"`. For more information about Redis commands, see [https://redis.io/commands](https://redis.io/commands). ## Related content - [How can I run Redis commands?](cache-development-faq.yml#how-can-i-run-redis-commands-) - [Monitor Azure Cache for Redis](../redis/monitor-cache.md)