- RTI Connext Micro C API Version 4.3.0 Copyright © Thu May 28 2026
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RTI Connext Micro C API Version 4.3.0
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<<cert>> Resource limits that apply only to DDS_DomainParticipant instances. More...
#include <dds_c_infrastructure.h>
Data Fields | |
| DDS_Long | local_writer_allocation |
| The maximum number of local Writers that can be created. | |
| DDS_Long | local_reader_allocation |
| The maximum number of local Readers that can be created. | |
| DDS_Long | local_publisher_allocation |
| The maximum number of local Publishers that can be created. | |
| DDS_Long | local_subscriber_allocation |
| The maximum number of local Subscribers that can be created. | |
| DDS_Long | local_topic_allocation |
| The maximum number of topics that can be created. | |
| DDS_Long | local_type_allocation |
| The maximum number of local types that can be registered with this DomainParticipant. | |
| DDS_Long | remote_participant_allocation |
| The maximum number of remote participants that can be discovered by this DomainParticipant. | |
| DDS_Long | remote_writer_allocation |
| The maximum number of remote writers that can be discovered by this DomainParticipant. | |
| DDS_Long | remote_reader_allocation |
| The maximum number of remote readers that can be discovered by this DomainParticipant. | |
| DDS_Long | matching_writer_reader_pair_allocation |
| The maximum number of matching local writer and remote/local reader pairs. | |
| DDS_Long | max_receive_ports |
| Maximum number of addresses that can be listened on. | |
| DDS_Long | max_destination_ports |
| Maximum number of unique destination addresses that a participant can reach. | |
| DDS_UnsignedLong | shmem_ref_transfer_mode_max_segments |
| Maximum number of segments created by all DDS_DataWriter entities belonging to a DDS_DomainParticipant. | |
| DDS_Long | participant_user_data_max_length |
| Maximum length of user data in DDS_DomainParticipantQos and DDS_ParticipantBuiltinTopicData. | |
| DDS_Long | participant_user_data_max_count |
| Maximum number of unique user data sequences allowed across DomainParticipants (the local DDS_DomainParticipantQos and discovered participants). | |
| DDS_Long | topic_data_max_length |
| Maximum length of topic data in DDS_TopicQos, DDS_PublicationBuiltinTopicData, and DDS_SubscriptionBuiltinTopicData. | |
| DDS_Long | topic_data_max_count |
| Maximum number of unique topic data sequences allowed in the DDS_TopicQos across all local topics, discovered publications, and discovered subscriptions. | |
| DDS_Long | publisher_group_data_max_length |
| Maximum length of group data in DDS_PublisherQos and DDS_PublicationBuiltinTopicData. | |
| DDS_Long | publisher_group_data_max_count |
| Maximum number of unique group data sequences allowed in the DDS_PublisherQos across all local publishers and discovered publications. | |
| DDS_Long | subscriber_group_data_max_length |
| Maximum length of group data in DDS_SubscriberQos and DDS_SubscriptionBuiltinTopicData. | |
| DDS_Long | subscriber_group_data_max_count |
| Maximum number of unique group data sequences allowed in the DDS_SubscriberQos across all local subscribers and discovered subscriptions. | |
| DDS_Long | writer_user_data_max_length |
| Maximum length of user data in DDS_DataWriterQos and DDS_PublicationBuiltinTopicData. | |
| DDS_Long | writer_user_data_max_count |
| Maximum number of unique user data sequences allowed in the DDS_DataWriterQos across all local DDS_DataReader entities and discovered publications. | |
| DDS_Long | reader_user_data_max_length |
| Maximum length of user data in DDS_DataReaderQos and DDS_SubscriptionBuiltinTopicData. | |
| DDS_Long | reader_user_data_max_count |
| Maximum number of unique user data sequences allowed in the DDS_DataReaderQos across all local DDS_DataReader entities and discovered subscriptions. | |
| DDS_Long | max_partitions |
| The maximum number of elements in the DDS_PartitionQosPolicy. | |
| DDS_Long | max_partition_cumulative_characters |
| The maximum number of combined characters across all DDS_PartitionQosPolicy PARTITION.name sequence elements, including the NUL characters. | |
| DDS_Long | max_partition_string_size |
| The maximum number of 8-bit characters in a PARTITION.name element, including the NUL termination. | |
| DDS_Long | max_partition_string_allocation |
| The maximum number of 8-bit characters reserved for PARTITION.name strings to allocate for the PARTITION DDS_PartitionQosPolicy. | |
<<cert>> Resource limits that apply only to DDS_DomainParticipant instances.
This QoS policy is an extension to the DDS standard.
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::local_writer_allocation |
The maximum number of local Writers that can be created.
This resource-limit limits the maximum number of DDS_DataWriter entities that can be created with the DDS_Publisher_create_datawriter() API within a single DDS_DomainParticipant across all DDS_Publisher entities.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::local_reader_allocation |
The maximum number of local Readers that can be created.
This resource-limit limits the maximum number of DDS_DataReader entities that can be created with the DDS_Subscriber_create_datareader() API within a single DDS_DomainParticipant across all DDS_Subscriber entities.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::local_publisher_allocation |
The maximum number of local Publishers that can be created.
This resource-limit limits the maximum number of DDS_Publisher entities that can be created within a DDS_DomainParticipant with the DDS_DomainParticipant_create_publisher() API.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::local_subscriber_allocation |
The maximum number of local Subscribers that can be created.
This resource-limit limits the maximum number of DDS_Subscriber entities that can be created within a DDS_DomainParticipant with the DDS_DomainParticipant_create_subscriber() API.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::local_topic_allocation |
The maximum number of topics that can be created.
This resource-limit limits the maximum number of unique DDS_Topic instances that can be created within a single DDS_DomainParticipant with the DDS_DomainParticipant_create_topic() API.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::local_type_allocation |
The maximum number of local types that can be registered with this DomainParticipant.
This resource-limit limits the maximum number of unique ::DDS_TypePluginI instances that can be registered locally within a single DDS_DomainParticipant with the FooTypeSupport_register_type() API.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::remote_participant_allocation |
The maximum number of remote participants that can be discovered by this DomainParticipant.
This resource-limit limits the maximum number of DDS_DomainParticipant instances that can be discovered by a local DDS_DomainParticipant.
The DPDE discovery plugin is on a first-discovered, first-served basis, and the only way to limit discovery is careful use of peer addresses. The DPSE discovery plugin limits the discovery to those that have been asserted based on the DomainParticipant name using DPSE_RemoteParticipant_assert
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::remote_writer_allocation |
The maximum number of remote writers that can be discovered by this DomainParticipant.
This resource-limit limits the maximum number of remote DDS_DataWriter entities that can be discovered by a local DDS_DomainParticipant. Note that a remote DDS_DataWriter cannot be discovered until its parent DDS_DomainParticipant has been discovered.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::remote_reader_allocation |
The maximum number of remote readers that can be discovered by this DomainParticipant.
This resource-limit limits the maximum number of remote DDS_DataReader entities that can be discovered by a local DomainParticipant. Note that a remote DDS_DataReader cannot be discovered until its parent DDS_DomainParticipant has been discovered.
[default] 1
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::matching_writer_reader_pair_allocation |
The maximum number of matching local writer and remote/local reader pairs.
When RTI Connext DDS Micro discovers DDS entities using a DDS discovery protocol, such as DPSE (Dynamic Participant Static Endpoint) or DPDE (Dynamic Participant Dynamic Endpoint), it matches the discovered entities with the locally created DDS_DataReader entities and DDS_DataWriter entities. For each match, either a local DDS_DataWriter matching a remote DDS_DataReader or a local DDS_DataReader matching a remote DDS_DataWriter, internal state must be managed.
A match, in this context, is defined as being able to receive packets sent from a DDS_DataReader to a DDS_DataWriter, or from a DDS_DataWriter to a DDS_DataReader:
This resource-limit limits the maximum number of matches that can be managed. When this resource limit is reached, no further matching can occur, even if new DDS_DataReader and DDS_DataWriter entities are discovered.
A simple rule of thumb is to set this resource limit to:
This assumes that each DDS_DataReader and DDS_DataWriter matches one DDS_DataWriter and DDS_DataReader respectively for each discovered participant. However, this may over-allocate resources.
[default] 32
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::max_receive_ports |
Maximum number of addresses that can be listened on.
RTI Connext DDS Micro listens for discovery data and user data on different transports as specified by the user. This resource-limit limits the maximum number of addresses that can be listened on. As a rule of thumb, this resource limit can be determined as follows: - A user-traffic unicast port counts as 1. - A meta-traffic unicast port counts as 1. - A user-traffic multicast address counts as 1. - A meta-traffic multicast address counts as 1.
Consider the typical case with the UDP transport, using unicast and multicast for discovery data and unicast for user data:
Thus, this requires 3 resources.
Consider a case with the UDP transport, using unicast and multicast for discovery data and user data: - Discovery data needs two ports. - User data needs two ports.
Thus, this requires 4 resources.
Consider a case with the UDP transport, using unicast and 2 multicast addresses each for discovery data and user data:
Thus, this requires 6 resources.
The default value has been set to cover most cases. This resource-limit should only be changed if a lot of interfaces are supported (increase it) or if memory is extremely limited (decrease it).
[default] 8
[range] [1, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::max_destination_ports |
Maximum number of unique destination addresses that a participant can reach.
RTI Connext DDS Micro maintains a table of destination addresses that it can send to based on information queried from the registered transports. This resource limit is difficult to give a precise rule for how to determine, since it is transport dependent. However, as a rule of thumb, the following is true: - Each network that can be reached directly by the transport requires 1 resource. - If multicast is supported, it counts as 1 resource. - If the transport is the default transport (by default, UDP is), it counts as one address.
Consider a typical Linux computer with 2 network interfaces, eth0 and lo, with support for multicast:
This requires 4 resources.
Consider a typical embedded computer with 1 network interface, eth0, with no support for multicast:
This requires 2 resources.
The default value has been set to cover most cases. This resource-limit should only be changed if a lot of interfaces are supported (increase it) or if memory is extremely limited (decrease it).
[default] 8
[range] [1, INT_MAX]
| DDS_UnsignedLong DDS_DomainParticipantResourceLimitsQosPolicy::shmem_ref_transfer_mode_max_segments |
Maximum number of segments created by all DDS_DataWriter entities belonging to a DDS_DomainParticipant.
[default] 500
[range] [0,100000] but in practice, this value will be limited by the system-wide maximum number of shared memory segments. On a Linux machine, this value is provided by the kernel parameter shmmni.
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::participant_user_data_max_length |
Maximum length of user data in DDS_DomainParticipantQos and DDS_ParticipantBuiltinTopicData.
[default] 0
[range] [0, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::participant_user_data_max_count |
Maximum number of unique user data sequences allowed across DomainParticipants (the local DDS_DomainParticipantQos and discovered participants).
For example, if a discovered participant has the same user data as the local participant, then that unique sequence only counts once against this resource-limit.
[default] DDS_SIZE_AUTO
[range] [0, INT_MAX] or DDS_SIZE_AUTO
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::topic_data_max_length |
Maximum length of topic data in DDS_TopicQos, DDS_PublicationBuiltinTopicData, and DDS_SubscriptionBuiltinTopicData.
[default] 0
[range] [0, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::topic_data_max_count |
Maximum number of unique topic data sequences allowed in the DDS_TopicQos across all local topics, discovered publications, and discovered subscriptions.
For example, if a local topic has the same topic data as the topic of a discovered publication or subscription, then that unique sequence only counts once against this resource-limit.
[default] DDS_SIZE_AUTO
[range] [0, INT_MAX] or DDS_SIZE_AUTO
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::publisher_group_data_max_length |
Maximum length of group data in DDS_PublisherQos and DDS_PublicationBuiltinTopicData.
[default] 0
[range] [0, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::publisher_group_data_max_count |
Maximum number of unique group data sequences allowed in the DDS_PublisherQos across all local publishers and discovered publications.
For example, if a local publisher has the same group data as a discovered publication, then that unique sequence only counts once against this resource-limit.
[default] DDS_SIZE_AUTO
[range] [0, INT_MAX] or DDS_SIZE_AUTO
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::subscriber_group_data_max_length |
Maximum length of group data in DDS_SubscriberQos and DDS_SubscriptionBuiltinTopicData.
[default] 0
[range] [0, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::subscriber_group_data_max_count |
Maximum number of unique group data sequences allowed in the DDS_SubscriberQos across all local subscribers and discovered subscriptions.
For example, if a local subscriber has the same group data as a discovered subscription, then that unique sequence only counts once against this resource-limit.
[default] DDS_SIZE_AUTO
[range] [0, INT_MAX] or DDS_SIZE_AUTO
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::writer_user_data_max_length |
Maximum length of user data in DDS_DataWriterQos and DDS_PublicationBuiltinTopicData.
[default] 0
[range] [0, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::writer_user_data_max_count |
Maximum number of unique user data sequences allowed in the DDS_DataWriterQos across all local DDS_DataReader entities and discovered publications.
For example, if a local DDS_DataWriter has the same user data as a discovered publication, then that unique sequence only counts once against this resource-limit.
[default] DDS_SIZE_AUTO
[range] [0, INT_MAX] or DDS_SIZE_AUTO
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::reader_user_data_max_length |
Maximum length of user data in DDS_DataReaderQos and DDS_SubscriptionBuiltinTopicData.
[default] 0
[range] [0, INT_MAX]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::reader_user_data_max_count |
Maximum number of unique user data sequences allowed in the DDS_DataReaderQos across all local DDS_DataReader entities and discovered subscriptions.
For example, if a local DDS_DataReader has the same user data as a discovered subscription, then that unique sequence only counts once against this resource-limit.
[default] DDS_SIZE_AUTO
[range] [0, INT_MAX] or DDS_SIZE_AUTO
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::max_partitions |
The maximum number of elements in the DDS_PartitionQosPolicy.
This setting is made on a per DomainParticipant basis; it cannot be set individually on a per Publisher/Subscriber basis. However, the limit is enforced and applies per Publisher/Subscriber.
This value cannot exceed 64.
[default] 64
[range] [0,64]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::max_partition_cumulative_characters |
The maximum number of combined characters across all DDS_PartitionQosPolicy PARTITION.name sequence elements, including the NUL characters.
The maximum number of combined characters should account for a terminating NULL ('\0') character for each partition name string.
This setting is made on a per DomainParticipant basis; it cannot be set individually on a per Publisher/Subscriber basis. However, the limit is enforced and applies per Publisher/Subscriber.
This value cannot exceed 256.
[default] 256
[range] [0,256]
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::max_partition_string_size |
The maximum number of 8-bit characters in a PARTITION.name element, including the NUL termination.
[default] DDS_LENGTH_UNLIMITED
[range] DDS_LENGTH_UNLIMITED or greater than 0
| DDS_Long DDS_DomainParticipantResourceLimitsQosPolicy::max_partition_string_allocation |
The maximum number of 8-bit characters reserved for PARTITION.name strings to allocate for the PARTITION DDS_PartitionQosPolicy.
If max_partition_string_allocation is DDS_LENGTH_UNLIMITED then memory will be allocated and freed during operation.
This setting is made on a per DomainParticipant basis; it cannot be set individually on a per Publisher/Subscriber basis. However, the limit is enforced and applies per Publisher/Subscriber.
[default] DDS_LENGTH_UNLIMITED
[range] DDS_LENGTH_UNLIMITED or greater than 1