here - OSTA - Optical Storage Technology Association

the offset and length of a partition within physical space is specified by a Partition
Descriptor (see 2.2.14). A sparable partition shall begin and end on a packet boundary.
The sparing table further specifies an exception list of logical to physical mappings. All
mappings are one packet in length. The packet size is specified in the sparable partition
map.
Available sparing areas may be anywhere on the media, either inside or outside of a
partition. If located inside a partition, sparable space shall be marked as allocated and
shall be included in the Non-Allocatable Space Stream. The mapped locations should be
filled in at format time; the original locations are assigned dynamically as errors occur.
Each sparing table shall be structured as shown below.
Sparing Table layout
BP Length Name Contents
0 16 Descriptor Tag tag = 0
16 32 Sparing Identifier EntityID
48 2 Reallocation Table Length (=RT_L) Uint16
50 2 Reserved #00 bytes
52 4 Sequence Number Uint32
56 8*RT_L Map Entry Map Entries
This structure may be larger than a single sector if necessary.
• Descriptor Tag
Contains a Tag Identifier of 0, which indicates that the format of the Descriptor Tag is not
specified by ECMA 167. All other fields of the Descriptor Tag shall be valid, as if the Tag
Identifier were one of the values defined by ECMA 167.
• Sparing Identifier:
• Flags = 0
• Identifier = *UDF Sparing Table
• IdentifierSuffix is recorded as defined in UDF 2.1.5
• Reallocation Table Length
Indicates the number of entries in the Map Entry table.
• Sequence Number
Contains a number that shall be incremented each time the sparing table is updated.
• Map Entry
A map entry is described in the table below. Maps shall be sorted in ascending order by the
Original Location field.
UDF 2.01
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