# MIGRATE ```json metadata { "schema_version": 2, "title": "MIGRATE", "description": "Atomically transfers a key from one Redis instance to another.", "categories": ["docs","develop","stack","oss","rs","rc","oss","kubernetes","clients"], "arguments": [{"display_text":"host","name":"host","type":"string"},{"display_text":"port","name":"port","type":"integer"},{"arguments":[{"display_text":"key","key_spec_index":0,"name":"key","type":"key"},{"display_text":"empty-string","name":"empty-string","token":"","type":"pure-token"}],"name":"key-selector","type":"oneof"},{"display_text":"destination-db","name":"destination-db","type":"integer"},{"display_text":"timeout","name":"timeout","type":"integer"},{"display_text":"copy","name":"copy","optional":true,"since":"3.0.0","token":"COPY","type":"pure-token"},{"display_text":"replace","name":"replace","optional":true,"since":"3.0.0","token":"REPLACE","type":"pure-token"},{"arguments":[{"display_text":"password","name":"auth","since":"4.0.7","token":"AUTH","type":"string"},{"arguments":[{"display_text":"username","name":"username","type":"string"},{"display_text":"password","name":"password","type":"string"}],"name":"auth2","since":"6.0.0","token":"AUTH2","type":"block"}],"name":"authentication","optional":true,"type":"oneof"},{"display_text":"key","key_spec_index":1,"multiple":true,"name":"keys","optional":true,"since":"3.0.6","token":"KEYS","type":"key"}], "syntax_fmt": "MIGRATE host port \u003ckey | \"\"\u003e destination-db timeout [COPY] [REPLACE]\n [AUTH password | AUTH2 username password] [KEYS key [key ...]]", "complexity": "This command actually executes a DUMP+DEL in the source instance, and a RESTORE in the target instance. See the pages of these commands for time complexity. Also an O(N) data transfer between the two instances is performed.", "group": "generic", "command_flags": ["write","movablekeys"], "acl_categories": ["@keyspace","@write","@slow","@dangerous"], "since": "2.6.0", "arity": -6, "key_specs": [{"RW":true,"access":true,"begin_search":{"spec":{"index":3},"type":"index"},"delete":true,"find_keys":{"spec":{"keystep":1,"lastkey":0,"limit":0},"type":"range"}},{"RW":true,"access":true,"begin_search":{"spec":{"keyword":"KEYS","startfrom":-2},"type":"keyword"},"delete":true,"find_keys":{"spec":{"keystep":1,"lastkey":-1,"limit":0},"type":"range"},"incomplete":true}], "tableOfContents": {"sections":[{"id":"required-arguments","title":"Required arguments"},{"id":"optional-arguments","title":"Optional arguments"},{"children":[{"id":"migrating-multiple-keys-with-a-single-command-call","title":"Migrating multiple keys with a single command call"}],"id":"details","title":"Details"},{"id":"redis-software-and-redis-cloud-compatibility","title":"Redis Software and Redis Cloud compatibility"},{"id":"return-information","title":"Return information"}]} , "codeExamples": [] } ``` Atomically transfer a key from a source Redis instance to a destination Redis instance. On success the key is deleted from the original instance and is guaranteed to exist in the target instance. The command is atomic and blocks the two instances for the time required to transfer the key, at any given time the key will appear to exist in a given instance or in the other instance, unless a timeout error occurs. In 3.2 and above, multiple keys can be pipelined in a single call to `MIGRATE` by passing the empty string ("") as key and adding the `KEYS` clause. ## Required arguments
host The hostname or IP address of the destination Redis instance.
port The port of the destination Redis instance.
key | "" The key to migrate, or an empty string (`""`) when migrating multiple keys with the `KEYS` option.
destination-db The database index to migrate the key into on the destination instance.
timeout The maximum idle time for the transfer, in milliseconds.
## Optional arguments
COPY Do not remove the key from the local instance.
REPLACE Replace an existing key on the destination instance.
AUTH password Authenticate to the destination instance with the given password. `AUTH` and `AUTH2` are mutually exclusive.
AUTH2 username password Authenticate to the destination instance with the given username and password (ACL-style auth, Redis 6 or later).
KEYS key [key ...] Migrate all the listed keys. Use this when the key argument is an empty string (`""`).
## Details The command internally uses [`DUMP`](https://redis.io/docs/latest/commands/dump) to generate the serialized version of the key value, and [`RESTORE`](https://redis.io/docs/latest/commands/restore) in order to synthesize the key in the target instance. The source instance acts as a client for the target instance. If the target instance returns OK to the [`RESTORE`](https://redis.io/docs/latest/commands/restore) command, the source instance deletes the key using [`DEL`](https://redis.io/docs/latest/commands/del). The timeout specifies the maximum idle time in any moment of the communication with the destination instance in milliseconds. This means that the operation does not need to be completed within the specified amount of milliseconds, but that the transfer should make progresses without blocking for more than the specified amount of milliseconds. `MIGRATE` needs to perform I/O operations and to honor the specified timeout. When there is an I/O error during the transfer or if the timeout is reached the operation is aborted and the special error - `IOERR` returned. When this happens the following two cases are possible: * The key may be on both the instances. * The key may be only in the source instance. It is not possible for the key to get lost in the event of a timeout, but the client calling `MIGRATE`, in the event of a timeout error, should check if the key is _also_ present in the target instance and act accordingly. When any other error is returned (starting with `ERR`) `MIGRATE` guarantees that the key is still only present in the originating instance (unless a key with the same name was also _already_ present on the target instance). If there are no keys to migrate in the source instance `NOKEY` is returned. Because missing keys are possible in normal conditions, from expiry for example, `NOKEY` isn't an error. ### Migrating multiple keys with a single command call Starting with Redis 3.0.6 `MIGRATE` supports a new bulk-migration mode that uses pipelining in order to migrate multiple keys between instances without incurring in the round trip time latency and other overheads that there are when moving each key with a single `MIGRATE` call. In order to enable this form, the `KEYS` option is used, and the normal *key* argument is set to an empty string. The actual key names will be provided after the `KEYS` argument itself, like in the following example: MIGRATE 192.168.1.34 6379 "" 0 5000 KEYS key1 key2 key3 When this form is used the `NOKEY` status code is only returned when none of the keys is present in the instance, otherwise the command is executed, even if just a single key exists. ## Redis Software and Redis Cloud compatibility | Redis
Software | Redis
Cloud | Notes | |:----------------------|:-----------------|:------| | ❌ Standard
❌ Active-Active | ❌ Standard
❌ Active-Active | | ## Return information **RESP2:** One of the following: * [Simple string reply](../../develop/reference/protocol-spec#simple-strings): `OK` on success. * [Simple string reply](../../develop/reference/protocol-spec#simple-strings): `NOKEY` when no keys were found in the source instance. **RESP3:** One of the following: * [Simple string reply](../../develop/reference/protocol-spec#simple-strings): `OK` on success. * [Simple string reply](../../develop/reference/protocol-spec#simple-strings): `NOKEY` when no keys were found in the source instance.