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    :Limits

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    :Limits

    Last Updated:Nov 23, 2023

    This topic describes the limits of data types and specific features of Tair.

    Item

    Description

    LIST data type

    The number of lists and the number of elements in a list are unlimited. A single element can be a maximum of 512 MB in size.

    We recommend that you keep the number of elements in a list smaller than 8,192 and ensure that the overall size of the list does not exceed 1 MB.

    SET data type

    The number of sets and the number of elements in a set are unlimited. A single element can be a maximum of 512 MB in size.

    We recommend that you keep the number of elements in a set smaller than 8,192 and ensure that the overall size of the set does not exceed 1 MB.

    Sorted Set data type

    The number of sorted sets and the number of elements in a sorted set are unlimited. A single element can be a maximum of 512 MB in size.

    We recommend that you keep the number of elements in a sorted set smaller than 8,192 and ensure that the overall size of the sorted set does not exceed 1 MB.

    HASH data type

    The number of hashes and the number of elements in a hash are unlimited. A single element can be a maximum of 512 MB in size.

    We recommend that you keep the number of elements in a hash smaller than 8,192 and ensure that the overall size of the hash does not exceed 1 MB.

    Number of databases

    Each instance supports up to 256 databases.

    Note

    • The total size of data stored in all databases of an instance depends on the memory size of the instance.

    • The system automatically assigns memory to a single database based on memory usage of the database. The upper limit of assigned memory is the instance memory. For example, if Database 0 occupies all memory, other databases have no data.

    Supported Redis commands

    For more information, see Overview.

    Monitoring and alerting

    To configure monitoring and alerting for Tair, log on to the CloudMonitor console. For more information, see Alerting settings.

    We recommend that you set alerts for the following metrics: instance failures, instance failover, connection usage, failed operations, capacity usage, write bandwidth usage, and read bandwidth usage.

    Policy to delete expired data

    • Automatic deletion: The system periodically detects and deletes expired keys in the background.

    • Triggered deletion: The system deletes expired keys when you access these keys.

    Mechanism to recycle idle connections

    Tair does not automatically recycle idle connections. You can manage the connections.

    Policy for data persistence

    Tair uses the AOF_FSYNC_EVERYSEC policy to run the fsync command at a one-second interval.