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    Data Transmission Service:One-way synchronization between Tair (Redis-compatible) instances

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    Data Transmission Service:One-way synchronization between Tair (Redis-compatible) instances

    Last Updated:Jun 22, 2026

    DTS provides one-way synchronization for Redis databases, enabling scenarios like active geo-redundancy and geo-disaster recovery. This topic shows you how to configure a one-way synchronization job between Tair instances.

    Prerequisites

    • A destination Tair (Redis OSS-Compatible) instance has been created. See Step 1: Create an instance.

    • The storage space of the destination Tair (Redis OSS-Compatible) instance must be greater than the used storage space of the source Tair (Redis OSS-Compatible) instance.

    Usage notes

    Type

    Description

    Source database limitations

    • DTS inserts a key prefixed with DTS_REDIS_TIMESTAMP_HEARTBEAT into the source database to record update timestamps. For clusters, this key is inserted into each shard. The key is filtered during synchronization and expires after the task completes.

    • If the source database is a read-only instance or the DTS account does not have write (SETEX) permissions, the reported latency may be inaccurate.

    • To ensure connection stability, increase the value of the repl-backlog-size parameter in the redis.conf file.

    • Do not run FLUSHDB or FLUSHALL on the source database. This causes data inconsistency between the source and destination.

    • If some keys in the source database have an expiration policy, they may not be deleted immediately upon expiry. The key count in the destination (viewable with info) may be lower than in the source.

    • If the source instance is a Tair (Enterprise Edition) instance whose Storage Medium is Persistent Memory, ensure that the appendonly parameter is set to yes as described in Steps.

    • If the source database is a self-managed Redis instance:

      • When synchronizing from a standalone to a cluster Redis instance, Redis clusters allow a single command to operate on only one slot. Multi-key operations on keys in different slots return the following error:

        CROSSSLOT Keys in request don't hash to the same slot

        To prevent task interruptions, perform only single-key operations during DTS synchronization.

    • If the source Redis instance uses extended modules such as RedisJSON, RediSearch, RedisBloom, RedisTimeSeries, RedisGraph, RedisAI, RedisGears, RedisCell, RediSQL, redis-tdigest, or RedisCompat, DTS cannot parse their RDB storage formats and the task fails.

    • If the source is a child instance of a Tair (Enterprise Edition) Global Distributed Cache, DTS can synchronize data only from the selected child instance. Data from other child instances in the group is not synchronized.

    Other limitations

    • For a self-managed Redis source, set repl-timeout to 600 seconds by running config set repl-timeout 600. Increase the repl-timeout value if the source contains a large amount of data.

    • Operations on the source or target Redis instance during synchronization, such as scaling, changing specifications, migrating availability zones, or changing the endpoint or port, can interrupt the task. DTS cannot obtain continuous log data or correct connection information. If this occurs, clear the synchronized data from the target before you reconfigure the task.

    • If the source or destination is a self-managed Redis (where Access Method is not Alibaba Cloud Instance) and its endpoint changes during synchronization (for example, due to a migration or primary/standby switchover), the task may experience retries, latency, or failures, and data inconsistency may occur. Monitor the task status and reconfigure it if abnormalities persist.

    • During an instance migration on a target Redis instance, such as a primary/standby switchover, data may be written only to memory and not replicated to the standby instance, which can lead to data loss.

    • To ensure compatibility, use the same version for the source and destination databases or synchronize from an earlier version to a later one.

    • During initial full data synchronization, DTS consumes read and write resources on the source and destination, which may increase load. Evaluate database performance beforehand and synchronize during off-peak hours.

    • During DTS synchronization, do not write data to the destination database from any source other than DTS. Otherwise, data inconsistency between the source and destination databases will result.

    • If the destination instance is a cluster and one of its shards reaches its memory limit, or if the destination instance runs out of storage space, the DTS task fails due to an out-of-memory (OOM) error.

    • If the destination runs out of memory, data eviction may cause inconsistency between the source and destination. The default maxmemory-policy for Tair (Redis OSS-Compatible) is volatile-lru, which does not affect task operation but may evict data.

      Set the destination eviction policy to noeviction to prevent data loss. With this policy, write operations fail and the task stops when memory is exhausted, but no data is evicted.

    • DTS does not currently support synchronization if the source or destination has Transparent Data Encryption (TDE) enabled.

    • Full data may be re-synchronized to the destination and cause data inconsistency under the following conditions:

      • A transient connection interruption occurs on the source or destination Redis instance, and resumable transmission fails.

      • A primary/standby switchover or a failover occurs on the source or destination Redis.

      • The endpoint of the source or destination Redis instance changes.

      • The synchronized objects of the DTS instance are modified.

    • If a Tair (Redis OSS-Compatible) instance has Transport Layer Security (TLS) encryption enabled, you must connect to it by using the SSL-encrypted method in DTS. TLSv1.3 is not supported. You cannot connect to an SSL-enabled Tair (Redis OSS-Compatible) instance by setting the Alibaba Cloud Instance to Alibaba Cloud Instance.

    • Restarting a synchronization instance that includes both full and incremental tasks may cause DTS to rerun both.

    • Restarting a synchronization instance may cause commands to execute more than once, leading to data inconsistency if non-idempotent commands such as INCRBY and LPUSH exist, or if full data re-synchronization is triggered.

    • If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters.

      Note

      Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

    Billing

    Type

    Fee

    Full data synchronization

    Free.

    Incremental data synchronization

    Charged. For details, see Billing overview.

    Synchronization topologies

    • One-way one-to-one synchronization

    • One-way one-to-many synchronization

    • One-way cascade synchronization

    For an introduction to each synchronization topology and its usage, see Synchronization topologies.

    Supported commands

    • APPEND

    • BITOP, BLPOP, BRPOP, and BRPOPLPUSH

    • DECR, DECRBY, and DEL

    • EVAL, EVALSHA, EXEC, EXPIRE, and EXPIREAT

    • GEOADD and GETSET

    • HDEL, HINCRBY, HINCRBYFLOAT, HMSET, HSET, and HSETNX

    • INCR, INCRBY, and INCRBYFLOAT

    • LINSERT, LPOP, LPUSH, LPUSHX, LREM, LSET, and LTRIM

    • MOVE, MSET, MSETNX, and MULTI

    • PERSIST, PEXPIRE, PEXPIREAT, PFADD, PFMERGE, and PSETEX

    • RENAME, RENAMENX, RESTORE, RPOP, RPOPLPUSH, RPUSH, and RPUSHX

    • SADD, SDIFFSTORE, SELECT, SET, SETBIT, SETEX, SETNX, SETRANGE, SINTERSTORE, SMOVE, SPOP, SREM, and SUNIONSTORE

    • ZADD, ZINCRBY, ZINTERSTORE, ZREM, ZREMRANGEBYLEX, ZUNIONSTORE, ZREMRANGEBYRANK, and ZREMRANGEBYSCORE

    • SWAPDB and UNLINK (supported only when the source Redis instance is version 4.0)

    • XADD, XCLAIM, XDEL, XAUTOCLAIM, XGROUP CREATECONSUMER, and XTRIM

    Note

    • The PUBLISH command is not supported.

    • DTS cannot guarantee the successful execution of a Lua script called with EVAL or EVALSHA during incremental data synchronization because the destination does not explicitly return an execution result.

    • When retransmitting list data using SYNC or PSYNC, DTS does not clear existing data in the destination, which may cause duplicate data.

    Permission requirements for database accounts

    Database

    Permissions and authorization

    Source Tair (Redis OSS-Compatible) instance

    Requires read permission. For the authorization method, see Create and manage accounts.

    Destination Tair (Redis OSS-Compatible) instance

    Requires read and write permissions. For the authorization method, see Create and manage accounts.

    Procedure

    1. Go to the data synchronization task list page in the destination region. You can do this in one of two ways.

      DTS console

      1. Log on to the DTS console.

      2. In the navigation pane on the left, click Data Synchronization.

      3. In the upper-left corner of the page, select the region where the synchronization instance is located.

      DMS console

      Note

      The actual steps may vary depending on the mode and layout of the DMS console. For more information, see Simple mode console and Customize DMS console layout and style.

      1. Log on to the DMS console.

      2. In the top menu bar, choose Data + AI > DTS (DTS) > Data Synchronization.

      3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.

    2. Click Create Task to open the task configuration page.

    3. Configure the source and destination databases.

      Section

      Parameter

      Description

      N/A

      Task Name

      DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.

      Source Database

      Select Existing Connection

      • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

        Note

        In the DMS console, this configuration item is Select a DMS database instance.

      • If you have not registered the database instance or do not need to use a registered instance, manually configure the database information below.

      Database Type

      Select Tair/Redis.

      Access Method

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the source Tair instance is located.

      Replicate Data Across Alibaba Cloud Accounts

      This example synchronizes data within the same Alibaba Cloud account. Select No.

      Instance ID

      Select the ID of the source Tair instance.

      Authentication Method

      Select an authentication method based on your requirements. In this example, Password Login is selected.

      Note

      • Only Redis 6.0 and later support Account + Password Login.

      • If you select Secret-free login, make sure that password-free access is enabled for the Redis database. For information about how to enable password-free access for a Tair (Redis OSS-Compatible) instance, see Enable password-free access over a VPC.

      Database Password

      Enter the password of the database account used to connect to the source Tair instance. For more information about the required account permissions, see Permissions required for database accounts.

      Note

      The database password must be in the <user>:<password> format. For example, if the custom username of the Redis instance is admin and the password is Rp829dlwa, enter admin:Rp829dlwa.

      Encryption

      Select Non-encrypted or SSL-encrypted based on your database instance requirements.

      Note

      If you are using a self-managed Redis instance (the Access Method is not Alibaba Cloud Instance) and you select SSL-encrypted, you must also upload a CA Certificate and enter the CA Certificate Password.

      Destination Database

      Select Existing Connection

      • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

        Note

        In the DMS console, this configuration item is Select a DMS database instance.

      • If you have not registered the database instance or do not need to use a registered instance, manually configure the database information below.

      Database Type

      Select Tair/Redis.

      Access Method

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination Tair instance is located.

      Replicate Data Across Alibaba Cloud Accounts

      This example synchronizes data within the same Alibaba Cloud account. Select No.

      Instance ID

      Select the ID of the destination Tair instance.

      Authentication Method

      Select an authentication method based on your requirements. In this example, Password Login is selected.

      Note

      • Only Redis 6.0 and later support Account + Password Login.

      • If you select Secret-free login, make sure that password-free access is enabled for the Redis database. For information about how to enable password-free access for a Tair (Redis OSS-Compatible) instance, see Enable password-free access over a VPC.

      Database Password

      Enter the password of the database account used to connect to the destination Tair instance. For more information about the required account permissions, see Permissions required for database accounts.

      Note

      The database password must be in the <user>:<password> format. For example, if the custom username of the Redis instance is admin and the password is Rp829dlwa, enter admin:Rp829dlwa.

      Encryption

      Select Non-encrypted or SSL-encrypted based on your database instance requirements.

      Note

      If you are using a self-managed Redis instance (the Access Method is not Alibaba Cloud Instance) and you select SSL-encrypted, you must also upload a CA Certificate and enter the CA Certificate Password.

    4. After completing the configuration, click Test Connectivity and Proceed at the bottom of the page.

      Note

      • Ensure that you add the CIDR blocks of the DTS servers (either automatically or manually) to the security settings of both the source and destination databases to allow access. For more information, see Add the IP address whitelist of DTS servers.

      • If the source or destination is a self-managed database (i.e., the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

    5. Configure the task objects.

      1. On the Configure Objects page, specify the objects to synchronize.

        Parameter

        Description

        Synchronization Types

        • Redis Open-Source Edition instances: Fixed as Full Data Synchronization + Incremental Data Synchronization. No manual selection is required.

        • Tair (Enterprise Edition) instances: Full Data Synchronization + Incremental Data Synchronization is selected by default. You can deselect Full Data Synchronization to perform incremental synchronization only.

        Synchronization Topology

        Select One-way Synchronization.

        Note

        This parameter is available only when both the source and destination instances are Tair (Enterprise Edition) instances.

        Processing Mode of Conflicting Tables

        • Precheck and Report Errors: Checks if the destination is empty. If the destination is empty, the precheck is successful. If the destination is not empty, an error is reported during the precheck, and the data synchronization job does not start.

        • Ignore Errors and Proceed: Skips the Check the existence of objects in the destination database. precheck.

          Warning

          If you select Ignore Errors and Proceed, source data overwrites destination data if the same key exists in both the source and destination. This may cause data loss in the destination. Select this option with caution.

        Source Objects

        In the Source Objects box, click the objects, and then click 向右 to move them to the Selected Objects box.

        Note

        You can select objects only at the database level. To synchronize data for specific keys within a database, use the data filtering feature in the Selected Objects pane.

        Selected Objects

        To specify a destination database (DB 0 to DB 255) or filter data by prefix, use the mapping or filtering features. In the Selected Objects pane, right-click the database to synchronize, and then configure the settings in the Edit Schema dialog box that appears. For more information, see Map object names and Specify filter conditions.

      2. Click Next: Advanced Settings.

        Parameter

        Description

        Dedicated Cluster for Task Scheduling

        By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.

        Retry Time for Failed Connections

        If the connection to the source or destination database fails after the synchronization task starts, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails.

        Note

        • If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances.

        • DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.

        Retry Time for Other Issues

        If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails.

        Important

        The value of Retry Time for Other Issues must be less than that of Retry Time for Failed Connections.

        Enable Throttling for Full Data Synchronization

        During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s).

        Note

        This parameter is available only when Synchronization Types includes Full Data Synchronization.

        Enable Throttling for Incremental Data Synchronization

        You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).

        Environment Tag

        You can select an environment tag to identify the instance. This is not required for this example.

        Extend Expiration Time of Destination Database Key

        Specifies the extended time period for which keys synchronized from the source database remain valid in the destination instance. To ensure data consistency, we recommend that you extend the key expiration time, especially if you use commands such as the following.

        Note

        In scenarios involving distributed locks, this setting may prevent locks from being released in a timely manner.

        EXPIRE key seconds
PEXPIRE key milliseconds
EXPIREAT key timestamp
PEXPIREAT key timestampMs

        Configure ETL

        Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values:

        Monitoring and Alerting

        Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts.

      3. Click Data Verification to configure a data verification task.

        To use the data verification feature, see Configure data verification.

    6. Save the task and perform a precheck.

      • To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.

      • If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

      Note

      • Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.

      • If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.

      • If the precheck generates warnings:

        • For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.

        • For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

    7. Purchase the instance.

      1. When the Success Rate reaches 100%, click Next: Purchase Instance.

      2. On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

        Category

        Parameter

        Description

        New Instance Class

        Billing Method

        • Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks.

        • Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.

        Resource Group Settings

        The resource group to which the instance belongs. The default is default resource group. For more information, see What is Resource Management?.

        Instance Class

        DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.

        Subscription Duration

        In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years.

        Note

        This option appears only when the billing method is Subscription.

      3. Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.

      4. Click Buy and Start. In the OK dialog box that appears, click OK.

        You can view the task progress on the Data Synchronization page.

        Note

        If your DTS instance is configured for both full and incremental data synchronization (meaning Synchronization Types includes both Full Data Synchronization and Incremental Data Synchronization), the task appears as Incremental Data Synchronization in the synchronization task list.