[Yandex Cloud documentation](../index.md) > [Yandex StoreDoc](index.md) > Inspections and recommendations

# Inspections and recommendations in Yandex StoreDoc 

Managed database clusters regularly undergo diagnostics to detect possible issues, increase the cluster's reliability, and improve its performance. The results of such checks are displayed as inspections under **Recommendations**. You can see notifications about successful checks and recommendations on eliminating discovered risks. The responsibility to troubleshoot any detected issues lies within the Yandex Cloud user's [remit](../overview/concepts/mdb-responsibilities.md).

All checks have a severity level:

* High level: Criteria of high cluster availability, significant risks of reduced performance, data loss risks. Such checks warrant special attention and require following the recommendations provided. 
* Moderate level: Possible risks of reduced performance, suboptimal memory and disk space usage.
* Low level: Potential risks and cluster operation limitations.

The list of recommendations is updated regularly. For each recommendation, the following timestamps are fixed: the date of the risk's first detection and the date of the most recent status update on this issue. If the recommendation seems to be excessive or incorrect, you can hide it, specifying a reason. Once the hiding period expires, the recommendation will automatically become available again if the issue persists.

Recommendations are available at the cluster, folder, and cloud levels and provide tips for all your resources. However, the absence of recommendations does not mean that your cluster is optimized: the list of checks gets continuously appended but still remains incomprehensive and cannot replace monitoring, since it is **targeted at detecting patterns rather than specific issues**. You can additionally run cluster performance diagnostics and analyze monitoring metrics.

Managing recommendations in Yandex StoreDoc requires the [managed-mongodb.editor role or higher](security/index.md).

## Available inspections in Yandex StoreDoc {#mmg-recommendations}

| **Category** | **Check** | **Risk** | **Severity** |
|---------------------|----------------------------------------------|-------------------------------------------------------------------------------------------------------|-----------------|
| Performance | CPU usage | [Risk of reduced performance](#storedoc_cpu_idle) | High         |
| High availability | Availability of replicas in a shard                       | [Risk of data loss and cluster unavailability in the event of a zone failure (lack of replicas)](#storedoc_ha_replics) | Low          |
| High availability | High cluster availability during zone failure | [Risk of data loss and cluster unavailability in the event of a zone failure](#storedoc_ha_geos) | High         |
| High availability | Allocating disk space | [Risk of cluster unavailability](#storedoc_disk_free_space) | High         |
| High availability | Memory allocation | [Lack of RAM](#storedoc_oom) | High         |
| High availability | Database version updates | [Database version is out of date](#storedoc_deprecated_version) | High         |
| High availability | Replication lag | [Risk of data loss](#storedoc_replication_lag) | Moderate       |
| High availability | Disk autoscaling feature | [Disk space autoscaling is limited](#storedoc_disk_autoscaling_limit) | Moderate       |

### Risk of reduced performance {#storedoc_cpu_idle}

**Description**

The host continuously uses all CPU resources, which may cause delays in query processing. Check the [load](operations/performance-diagnostics.md) and optimize your queries (which may include using the WebSQL [AI assistant](../websql/operations/ai-assistant.md)) or increase computing resources of the cluster.

**Action**

To increase the cluster's computing resources:

1. Navigate to **Yandex StoreDoc**.
1. Select your cluster and click ![image](../_assets/console-icons/pencil.svg) **Edit**.
1. Under **Resources**, select a host class with the required amount of vCPUs.
1. Click **Save changes**.

### Risk of data loss and cluster unavailability in the event of a zone (replica) failure {#storedoc_ha_replics}

**Description**

Your shards have no replicas, posing a risk of data loss and cluster unavailability. To ensure high availability, add replicas in a different zone for the specified shards.

**Action**

To migrate hosts from one availability zone to another, do the following:

1. [Create a subnet](../vpc/operations/subnet-create.md) in the target availability zone for the hosts.
1. Add a host to the cluster: in the [management console](https://console.yandex.cloud), select a folder.
1. [Navigate](https://console.yandex.cloud/link/storedoc) to **Yandex StoreDoc**.
1. Locate the Yandex StoreDoc cluster you need in the list, click its name, and select the **Hosts** tab.
1. Click ![image](../_assets/console-icons/plus.svg) **Create host**.
1. Specify the following host settings:

    * Target availability zone for your hosts.
    * New subnet.
    * To make the host accessible from outside Yandex Cloud, select **Public access**.

1. Click **Save**.
1. Delete the hosts in the source availability zone.

### Risk of data loss and cluster unavailability in the event of a zone failure {#storedoc_ha_geos}

**Description**

The current distribution of cluster hosts does not ensure fault protection in a single availability zone. Distribute replicas across different zones to ensure high availability.

{% note info %}

Single-host clusters are excluded from high availability testing: Yandex Cloud users are fully responsible for managing such a configuration.

{% endnote %}

**Action**

To add a host to a different zone:

1. Navigate to **Yandex StoreDoc**.
1. Select the cluster and open the **Hosts** tab.
1. Click **Create host**.
1. In the host settings, specify an alternative availability zone.
1. Finish configuring the host and click **Save**.

### Risk of cluster unavailability {#storedoc_disk_free_space}

**Description**

Your host is critically low on free space. Some operations may be disabled, while the whole cluster may become unavailable, i.e., switch to read-only mode. Increase the disk size or clear unused data.

**Action**

To increase the disk size:

1. Navigate to **Yandex StoreDoc**.
1. Select your cluster and click ![image](../_assets/console-icons/pencil.svg) **Edit**.
1. Under **Storage**, increase the disk size.
1. Click **Save changes**. 

### Not enough RAM {#storedoc_oom}

**Description**

The cluster is running out of RAM, which leads to slow performance or emergency shutdowns. Increase the cluster's RAM.

**Action**

To increase the amount of RAM:

1. Navigate to **Yandex StoreDoc**.
1. Select your cluster and click ![image](../_assets/console-icons/pencil.svg) **Edit**.
1. Under **Resources**, select a host class with the required amount of RAM.
1. Click **Save changes**.

### Database version is out of date {#storedoc_deprecated_version}

**Description**

The database version is out of date. Support for the version was officially discontinued. Clusters are running, but support is limited. We recommend upgrading to a supported version.

**Action**

To upgrade the database version:

1. Navigate to **Yandex StoreDoc**.
1. Select your cluster and click ![image](../_assets/console-icons/pencil.svg) **Edit**.
1. In the **Version** field, select Yandex StoreDoc.
1. Click **Save changes**.

### Risk of data loss {#storedoc_replication_lag}

**Description**

The host has a high replication lag, which may result in data loss. Check the load on the master node and replicas and optimize your requests or increase the cluster's computing resources.

**Action**

To increase the cluster's computing resources:

1. Navigate to **Yandex StoreDoc**.
1. Select your cluster and click ![image](../_assets/console-icons/pencil.svg) **Edit**.
1. Under **Resources**, select a host class with the required amount of vCPUs.
1. Click **Save changes**.

### Disk space autoscaling is limited {#storedoc_disk_autoscaling_limit}

**Description**

The disk autoscaling limit has been reached, so the cluster cannot increase its disk space when needed. Change the autoscaling settings in the cluster and increase the limit.

**Action**

To increase the disk size:

1. Navigate to **Yandex StoreDoc**.
1. Select your cluster and click ![image](../_assets/console-icons/pencil.svg) **Edit**.
1. Specify the maximum storage size after the expansion in the **Maximum storage size** field.
1. Click **Save changes**.