Tair (Redis® OSS-Compatible):One-way synchronization for cross-account instances

Before you start

Review these constraints before configuring the task:

• Version compatibility: Synchronize from an older version to a newer version only. Synchronizing from a newer version to an older version may cause compatibility issues.

• Cluster source — single-key commands only: If the source uses a cluster architecture, run only single-key commands during synchronization. Commands that operate on keys across different slots cause a CROSSSLOT Keys in request don't hash to the same slot error and break the sync link.

• Tair Enterprise Edition with Persistent Memory: If the source instance is a Tair Enterprise Edition instance using Persistent Memory as the storage medium, set the appendonly parameter to yes before starting. See Procedure.

• Transport Layer Security (TLS): If TLS is enabled on the source or destination instance, use an SSL-encrypted connection in DTS. TLSv1.3 is not supported. A TLS-enabled Tair instance cannot be connected as an Alibaba Cloud Instance type in DTS.

• Transparent Data Encryption (TDE): If TDE is enabled on either instance, DTS cannot be used for synchronization.

• Replication backlog size: To ensure a stable synchronization link, increase the value of the repl-backlog-size parameter in the redis.conf file.

• Self-managed Redis source — replication timeout: Run config set repl-timeout 600 to set the replication timeout to 600 seconds. Increase the value further if the source contains large amounts of data.

During synchronization

Keep these constraints in mind while the task is running:

• Do not write from other sources to the destination. Writing data from other sources to the destination causes data inconsistency between the source and destination.

• Destination memory policy: By default, Tair (Redis OSS-Compatible) instances use volatile-lru for data eviction. If the destination runs low on memory, data may be silently evicted without stopping the task, causing inconsistency. To prevent silent data loss, set maxmemory-policy to noeviction on the destination — if memory runs out, the task fails rather than evicting data. For details, see What is the default eviction policy?

• Destination cluster out of memory (OOM): If a shard in the destination cluster reaches its memory limit, or if the destination has insufficient storage, the sync task fails due to OOM.

• Expiration keys: Expired keys in the source may not be immediately deleted in the destination. The destination key count may be smaller than the source key count. Run the info command to verify key counts.

• DTS heartbeat key: DTS inserts a key prefixed with DTS_REDIS_TIMESTAMP_HEARTBEAT into the source database to track update timestamps. If the source database uses a cluster architecture, DTS inserts this key into each shard. This key is filtered during synchronization and expires when the task ends.

• Latency reporting: If the source is a read-only instance or the DTS account lacks SETEX permission, the reported latency may be inaccurate.

• Endpoint changes: If the source or destination endpoint changes during synchronization (for example, due to instance migration or failover), the task may retry, experience latency, fail, or cause data inconsistency. Check the task status promptly and reconfigure if needed.

• Scaling the source: If the source is scaled (shards added or removed) or its memory is scaled up during synchronization, reconfigure the task. Clear the destination data before reconfiguring to maintain consistency.

• Primary/replica failover on the destination: If a failover is triggered on the destination, data may be written only to memory and not persisted to the replica, which can cause data loss.

• Full re-synchronization triggers: The following events may cause all data to be re-synchronized to the destination, resulting in temporary data inconsistency:

  • A transient connection failure prevents the task from resuming from a breakpoint

  • A primary/replica failover occurs on the source or destination instance

  • The endpoint of the source or destination instance changes

  • The synchronization objects of the DTS instance are modified

• DTS instance failure recovery: If an instance fails, DTS helpdesk will try to recover the instance within 8 hours. Recovery may include restarting the DTS instance or adjusting its parameters (database parameters are not modified). For parameters that may be modified, see Modify instance parameters.

• Full and incremental restart: If a DTS instance that runs both full and incremental synchronization tasks is restarted, both tasks restart from the beginning.

Tair (Redis OSS-Compatible) Open-Source Edition

APPEND, BITOP, BLPOP, BRPOP, BRPOPLPUSH, DECR, DECRBY, DEL, EVAL, EVALSHA, EXEC, EXPIRE, EXPIREAT, GEOADD, GETSET, HDEL, HINCRBY, HINCRBYFLOAT, HMSET, HSET, HSETNX, INCR, INCRBY, INCRBYFLOAT, LINSERT, LPOP, LPUSH, LPUSHX, LREM, LSET, LTRIM, MOVE, MSET, MSETNX, MULTI, PERSIST, PEXPIRE, PEXPIREAT, PFADD, PFMERGE, PSETEX, RENAME, RENAMENX, RESTORE, RPOP, RPOPLPUSH, RPUSH, RPUSHX, SADD, SDIFFSTORE, SELECT, SET, SETBIT, SETEX, SETNX, SETRANGE, SINTERSTORE, SMOVE, SPOP, SREM, SUNIONSTORE, SWAPDB\*, UNLINK\*, XADD, XAUTOCLAIM, XCLAIM, XDEL, XGROUP CREATECONSUMER, XTRIM, ZADD, ZINCRBY, ZINTERSTORE, ZREM, ZREMRANGEBYLEX, ZUNIONSTORE, ZREMRANGEBYRANK, ZREMRANGEBYSCORE

\* SWAPDB and UNLINK are supported only when the source engine version is Redis 4.0.

Tair (Redis OSS-Compatible) Enterprise Edition

APPEND, BITOP, BLPOP, BRPOP, BRPOPLPUSH, DECR, DECRBY, DEL, EVAL, EVALSHA, EXEC, EXPIRE, EXPIREAT, GEOADD, GETSET, HDEL, HINCRBY, HINCRBYFLOAT, HMSET, HSET, HSETNX, INCR, INCRBY, INCRBYFLOAT, LINSERT, LPOP, LPUSH, LPUSHX, LREM, LSET, LTRIM, MOVE, MSET, MSETNX, MULTI, PERSIST, PEXPIRE, PEXPIREAT, PFADD, PFMERGE, PSETEX, RENAME, RENAMENX, RPOP, RPOPLPUSH, RPUSH, RPUSHX, SADD, SDIFFSTORE, SELECT, SET, SETBIT, SETEX, SETNX, SETRANGE, SINTERSTORE, SMOVE, SPOP, SREM, SUNIONSTORE, UNLINK, XADD, XAUTOCLAIM, XCLAIM, XDEL, XGROUP CREATECONSUMER, XTRIM, ZADD, ZINCRBY, ZINTERSTORE, ZREM, ZREMRANGEBYLEX, ZUNIONSTORE, ZREMRANGEBYRANK, ZREMRANGEBYSCORE

Commands with special behavior

Go to the Data Synchronization page

Create and configure the task

1. Click Create Task.

2. (Optional) Click New Configuration Page in the upper-right corner.

   Skip this step if the Back to Previous Version button is already displayed. The new and previous configuration pages may have different parameters — use the new version.

3. Configure the source and destination databases.

   Warning

   After you configure the source and destination databases, read the Limits displayed on the page before proceeding. Skipping this may cause task failures or data inconsistency.

   Source database

   Parameter	Value
   Task Name	DTS auto-generates a name. Specify a descriptive name for easier identification. The name does not need to be unique.
   Select Existing Connection	If the source instance is already registered with DTS, select it from the drop-down list — DTS populates the remaining fields automatically. Otherwise, configure the fields below.
   Database Type	Select Tair/Redis.
   Access Method	Select Alibaba Cloud Instance.
   Instance Region	Select the region of the source Tair instance.
   Replicate Data Across Alibaba Cloud Accounts	Select Yesalert notification settings.
   Alibaba Cloud Account	Enter the ID of the Alibaba Cloud account (primary account) that owns the source instance.
   RAM Role Name	Enter the name of the RAM role created in Step 1.
   Instance ID	Select the source Tair instance ID.
   Authentication Method	Select based on your requirements. This example uses Password Login. If you select Secret-free login, make sure that password-free access is enabled on the source instance. See Enable password-free access.
   Database Password	Enter credentials with read permission. For custom accounts, use the format <account>:<password> (for example, testaccount:Test1234). For the default account (username matches the instance ID), enter the password directly. Leave blank if no password is set. To reset the password, see Modify or reset the password.
   Encryption	Select Non-encrypted or SSL-encrypted. If you select SSL-encrypted for a self-managed Redis instance, upload a CA Certificate and enter a CA Key.

   Destination database

   Parameter	Value
   Select Existing Connection	If the destination instance is already registered with DTS, select it from the drop-down list. Otherwise, configure the fields below.
   Database Type	Select Tair/Redis.
   Access Method	Select Alibaba Cloud Instance.
   Instance Region	Select the region of the destination Tair instance.
   Replicate Data Across Alibaba Cloud Accounts	Select No — the cross-account setting applies only to the source side.
   Instance ID	Select the destination Tair instance ID.
   Authentication Method	Select based on your requirements. This example uses Password Login. If you select Secret-free login, make sure that password-free access is enabled. See Enable password-free access.
   Database Password	Enter credentials with read and write permissions. For custom accounts, use the format <account>:<password>. For the default account, enter the password directly. To reset, see Modify or reset the password.
   Encryption	Select Non-encrypted or SSL-encrypted.

4. Click Test Connectivity and Proceed.

   DTS server CIDR blocks must be added to the security allowlist of the source and destination instances. This can be done automatically or manually. For details, see Add DTS server IP addresses to a whitelist. If either instance is self-managed (access method is not Alibaba Cloud Instance), click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

5. Configure the objects to synchronize. In the Configure Objects step, set the following parameters:

   Parameter	Description
   Synchronization Types	By default, both Full Data Synchronization and Incremental Data Synchronization are selected. If you select Incremental Data Synchronization, also select Full Data Synchronization — the full sync runs first and provides the baseline for incremental sync.
   Synchronization Topology	Select One-way Synchronization. This parameter is available only when both the source and destination are Tair (Enterprise Edition) instances.
   Processing Mode of Conflicting Tables	Precheck and Report Errors: fails the precheck if data already exists in the destination. Ignore Errors and Proceed: skips the destination data existence check. Warning Choosing Ignore Errors and Proceed may cause data loss — source records overwrite destination records with the same keys.
   Source Objects	Select one or more databases from the Source Objects list and click the arrow icon to move them to Selected Objects. Only databases can be selected as sync objects — individual keys cannot.
   Selected Objects	To map DB 0–255 or filter by key prefix, right-click a database in Selected Objects and choose Edit Schema. See Map object names and Specify filter conditions. Object names cannot be mapped in bulk.

6. Click Next: Advanced Settings and configure the advanced parameters:

   Parameter	Description
   Dedicated Cluster for Task Scheduling	By default, DTS schedules the task to a shared cluster. To improve stability, purchase a dedicated cluster. See What is a DTS dedicated cluster.
   Retry Time for Failed Connections	How long DTS retries a failed connection before stopping the task. Valid values: 10–1,440 minutes. Default: 720. Set to a value greater than 30. If multiple tasks share the same source or destination, the shortest retry time applies. DTS charges you for the instance during retries — set this value based on your requirements and release the DTS instance promptly if the source or destination is released.
   Retry Time for Other Issues	How long DTS retries failed DDL or DML operations. Valid values: 1–1,440 minutes. Default: 10. Set to a value greater than 10. This value must be less than Retry Time for Failed Connections.
   Enable Throttling for Full Data Synchronization	Throttle read/write resource usage during full sync to reduce load on both instances. Configure Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s). Available only when Full Data Synchronization is selected.
   Enable Throttling for Incremental Data Synchronization	Throttle resource usage during incremental sync. Configure RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).
   Extend Expiration Time of Destination Database Key	Extend the TTL of keys synced to the destination by a specified number of seconds. Configure this when using expiration-based commands such as EXPIRE, PEXPIRE, EXPIREAT, or PEXPIREAT. Note In a distributed lock scenario, an extended TTL may delay lock release.
   Environment Tag	A label to identify the DTS instance. Optional.
   Configure ETL	Whether to enable extract, transform, and load (ETL) processing. Select Yes to configure ETL using the code editor. See Configure ETL in a data migration or data synchronization task. Select No to skip. For an overview, see What is ETL?
   Monitoring and Alerting	Whether to configure alerts for the sync task. Select Yes to set alert thresholds and notification contacts — alerts are triggered on task failure or when latency exceeds the threshold. See Configure monitoring and alerting when you create a DTS task.

7. Click Next Step: Data Verification to configure data verification (optional). See Configure a data verification task.

8. Save the task and run a precheck.

   • To preview the API parameters for this task configuration, hover over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.

   • Click Next: Save Task Settings and Precheck.

   DTS runs a precheck before starting the task. The task starts only after the precheck passes. - If the precheck fails, click View Details next to each failed item, fix the issue, and rerun the precheck. - If the precheck generates an alert that can be ignored, click Confirm Alert Details, click Ignore in the dialog box, then click Precheck Again. Ignoring alerts may result in data inconsistency.

9. Purchase an instance.

   1. Wait until the Success Rate reaches 100%, then click Next: Purchase Instance.

   2. On the purchase page, configure the billing and instance settings:

      Parameter	Description
      Billing Method	Subscription: pay upfront; more cost-effective for long-term use. Pay-as-you-go: billed hourly; release the instance when no longer needed to avoid charges.
      Resource Group Settings	The resource group for the sync instance. Default: default resource group. See What is Resource Management?
      Instance Class	Select a class based on the required synchronization speed. See Instance classes of data synchronization instances.
      Subscription Duration	Available only for the Subscription billing method. Options: 1–9 months, 1 year, 2 years, 3 years, or 5 years.

   3. Read and accept Data Transmission Service (Pay-as-you-go) Service Terms.

   4. Click Purchase and Start. In the confirmation dialog box, click OK. The task appears on the Data Synchronization page. If both full and incremental sync are configured, Incremental Data Synchronization is displayed as the current status after full sync completes.