Help Center> Distributed Cache Service> FAQ> Client and Network Connection> Why Is "ERR unknown command" Displayed When I Access a DCS Redis Instance Through a Redis Client?
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Why Is "ERR unknown command" Displayed When I Access a DCS Redis Instance Through a Redis Client?

The possible causes are as follows:

  1. The command is spelled incorrectly.

    As shown in the following figure, the error message is returned because the correct command for deleting a string should be del.

  2. A command available in a higher Redis version is run in a lower Redis version.

    As shown in the following figure, the error message is returned because a stream command (available in Redis 5.0) is run in Redis 3.0.

  3. Some commands are disabled.

    DCS Redis instance interfaces are fully compatible with the open-source Redis in terms of data access. However, for ease of use and security purposes, some operations cannot be initiated through Redis clients. For details about disabled commands, see Redis Command Compatibility.

  4. The following commands are disabled for cluster DCS Redis instances created before July 10, 2018. You can upgrade such an instance by submitting a service ticket.

    SINTER, SDIFF, SUNION, PFCOUNT, PFMERGE, SINTERSTORE, SUNIONSTORE, SDIFFSTORE, SMOVE, BLPOP, BRPOP, BRPOPLPUSH, ZUNIONSTORE, ZINTERSTORE, EVAL, EVALSHA, BITOP, RENAME, RENAMENX, RPOPLPUSH, MSETNX, SCRIPT LOAD, SCRIPT KILL, SCRIPT EXISTS, SCRIPT FLUSH

  5. The EVAL command is now compatible with recent single-node and master/standby DCS Redis instances. Older instances still do not support the command, and "ERR unknown command" will be displayed if EVAL is run. You can upgrade older instances by submitting a service ticket. Beware that during the upgrade, the Redis processes will be restarted and the services will be interrupted.