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# 5 Notes on low-level discovery

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#### Using LLD macros in user macro contexts

LLD macros may be used inside user macro context, for example, [in
trigger
prototypes](/manual/config/macros/user_macros_context#use_cases).

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#### Multiple LLD rules for the same item

It is possible to define several low-level discovery rules with the same discovery item.

To do that you need to define the Alias agent
[parameter](/manual/appendix/config/zabbix_agentd), allowing to use
altered discovery item keys in different discovery rules, for example
`vfs.fs.discovery[foo]`, `vfs.fs.discovery[bar]`, etc.

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#### Data limits for return values

There is no limit for low-level discovery rule JSON data if it is received directly by Zabbix server.
This is because the return values are processed without being stored in a database.

There is also no limit for custom low-level discovery rules.
However, if custom low-level discovery rule data is retrieved using a user parameter, the user parameter [return value limit](/manual/config/items/userparameters#command-result) applies.

If data has to go through Zabbix proxy, it has to store this data in the database.
In such a case, [database limits](/manual/config/items/item#text-data-limits) apply.

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