Structure of records and tables Table structure
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Overflow page of a duplicates table
Figure 61: Overflow page for a duplicates table
Depending on which page length was defined for a database, the length of an overflow page
may be 2048 bytes, 4000 bytes or 8096 bytes.
The following applies with respect to the lengths of entries for the record sequence number
(RSQ) and page index:
– In a 2048-byte overflow page, the RSQ entry is 3 bytes long, and the page index entry
is 8 bytes.
– In an overflow page of 4000 or 8096 bytes, the RSQ entry comprises 6 bytes, and th e
page index entry is 12 bytes.
A duplicates table is a special type of SEARCH key table in which key values that occur
several times are represented only once. When a part of a duplicates ta ble that contains
only one key value is to be extended to cover more than one page, UDS/SQL creates an
overflow page, in which the table line related to the key is continued. The connection to the
overflow page is not established via the table header but via the duplicates header.
DBTT Column
Status = 1
Beginning of
duplicated header
1
Length of
table line
RSQ
3/6
Duplicated header
Table line
2
RSQ
2
3/6
8
Page index entry
Nexxt overflow
page
Preceding overflow
page
No. of free bytes
3
3
2
Page header
Internal information
Page number for
table header
1
3
21
22
25/29
26/30
27/31
1
21
29
37
20
Free (only for 4000/
8096-byte pages)
25
4
8/12
Free