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# Redis Transactions Redis transactions allow multiple commands to be executed at once, with the following three important guarantees: * Batch operations are queued in a buffer before the EXEC command is sent. * After receiving the EXEC command, the transaction is executed. If any command within the transaction fails, the remaining commands are still executed. * During transaction execution, command requests submitted by other clients are not inserted into the transaction's command sequence. A transaction goes through the following three stages from start to execution: * Starting the transaction. * Queuing commands. * Executing the transaction. * * * ## Example Here is an example of a transaction. It starts with the **MULTI** command to begin a transaction, then queues multiple commands into the transaction, and finally uses the **EXEC** command to trigger the transaction, executing all commands within it together: redis 127.0.0.1:6379> MULTI OK redis 127.0.0.1:6379> SET book-name "Mastering C++ in 21 days" QUEUED redis 127.0.0.1:6379> GET book-name QUEUED redis 127.0.0.1:6379> SADD tag "C++" "Programming" "Mastering Series" QUEUED redis 127.0.0.1:6379> SMEMBERS tag QUEUED redis 127.0.0.1:6379> EXEC 1) OK 2) "Mastering C++ in 21 days" 3) (integer) 3 4) 1) "Mastering Series" 2) "C++" 3) "Programming" The execution of a single Redis command is atomic, but Redis does not add any mechanism to maintain atomicity for transactions. Therefore, the execution of a Redis transaction is not atomic. A transaction can be understood as a packaged batch execution script, but the batch commands are not atomic operations. The failure of a command in the middle will not cause a rollback of the commands already executed, nor will it prevent subsequent commands from being executed. > **This is the explanation from the official Redis documentation on (http://redis.io/topics/transactions):** > > > It's important to note that even when a command fails, all the other commands in the queue are processed – Redis will not stop the processing of commands. For example: redis 127.0.0.1:7000> multi OK redis 127.0.0.1:7000> set a aaa QUEUED redis 127.0.0.1:7000> set b bbb QUEUED redis 127.0.0.1:7000> set c ccc QUEUED redis 127.0.0.1:7000> exec 1) OK 2) OK 3) OK If the `set b bbb` command fails, the already successful `set a` will not be rolled back, and `set c` will still continue to execute. * * * ## Redis Transaction Commands The following table lists the commands related to Redis transactions: | No. | Command & Description | | --- | --- | | 1 | (#) Cancels the transaction, abandoning the execution of all commands within the transaction block. | | 2 | (#) Executes all commands within the transaction block. | | 3 | (#) Marks the beginning of a transaction block. | | 4 | (#) Cancels the WATCH command's monitoring of all keys. | | 5 | [WATCH key [key ...]](#) Monitors one (or more) keys. If this (or these) key(s) are modified by other commands before the transaction is executed, the transaction will be aborted. |