Restrictions

This section describes the restrictions on using DMS for RocketMQ.

**Table 1** DMS for RocketMQ restrictions
Item	Default Limit	Description
Maximum number of topics	Depends on the instance specifications. This limit cannot be changed.	When this limit is reached, no more topics can be created.
Maximum number of consumer groups	Depends on the instance specifications. This limit cannot be changed.	When this limit is reached, no more consumer groups can be created.
Message size	The maximum size of a message is 4 MB. The maximum size of a message attribute is 16 KB. The message size cannot be changed.	When this limit is reached, the message fails to be sent.
Message retention duration	Two days. This limit cannot be changed.	Messages can be retained for a maximum of two days and will be automatically deleted after two days.
Consumer offset reset	Two days. This limit cannot be changed.	You can reset the retrieval start position to any time within two days.
Delay of scheduled messages	The maximum delay is one year. This limit cannot be changed.	You can schedule messages to be delivered at any time within one year.