DMAPI configuration attributes

The System Management: Data Storage Management (XDSM) API Common Applications Environment (CAE) Specification C429, The Open Group, ISBN 1-85912-190-X defines a set of configuration attributes to be exported by each DMAPI implementation. These attributes specify which optional features are supported and give bounds on various resources.

The Data Management (DM) application can query the attribute values using the function dm_get_config. It can also query which events are supported, using the function dm_get_config_events.

The functions dm_get_config and dm_get_config_events receive a file handle from input arguments hanp and hlen. In GPFS, both functions ignore the handle, as the configuration is not dependent on the specific file or file system. This enables the DM application to query the configuration during initialization, when file handles may not yet be available.

Note: To ensure that the most current values are being used, the DM application should always query the configuration at runtime by using dm_get_config.

Table 1 shows the attribute values that are used in DMAPI for GPFS:

Table 1. DMAPI configuration attributes
Name	Value
DM_CONFIG_BULKALL	1
DM_CONFIG_CREATE_BY_HANDLE	0
DM_CONFIG_DTIME_OVERLOAD	1
DM_CONFIG_LEGACY	1
DM_CONFIG_LOCK_UPGRADE	1
DM_CONFIG_MAX_ATTR_ON_DESTROY	1022
DM_CONFIG_MAX_ATTRIBUTE_SIZE	1022
DM_CONFIG_MAX_HANDLE_SIZE	32
DM_CONFIG_MAX_MANAGED_REGIONS	32
DM_CONFIG_MAX_MESSAGE_DATA	4096
DM_CONFIG_OBJ_REF	0
DM_CONFIG_PENDING	0
DM_CONFIG_PERS_ATTRIBUTE	1
DM_CONFIG_PERS_EVENTS	1
DM_CONFIG_PERS_INHERIT_ATTRIBS	0
DM_CONFIG_PERS_MANAGED_REGIONS	1
DM_CONFIG_PUNCH_HOLE	1
DM_CONFIG_TOTAL_ATTRIBUTE_SPACE	7168
DM_CONFIG_WILL_RETRY	0

Attribute value DM_CONFIG_TOTAL_ATTRIBUTE_SPACE is per file. The entire space is available for opaque attributes. Non-opaque attributes (event list and managed regions) use separate space.