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System Architecture 2-109
Create a Database: What Happens on Disk
Allocate Disc Space
OnLine searches the linked list of chunk free-list maps in the dbspace,
looking for free space in which to create the system catalog tables. For each
table in turn, OnLine allocates eight contiguous pages, the size of the initial
extent of each system catalog table. The tables are created individually and
do not necessarily reside next to each other in the dbspace. They might be
located in different chunks. As adequate space is found for the initial extent
of each table, the pages are allocated and the associated chunk free-list page
is updated.
Track Systems Catalogs
An entry describing the database is added to the database tblspace in the root
dbspace. For each system catalog table, OnLine adds a one-page entry to the
tblspace tblspace in the dbspace. Figure 2-21 illustrates the relationship
between the database tblspace entry and the location of the systables table
for the database.
Figure 2-21
OnLine tracks
databases in the
database tblspace,
which resides in the
root dbspace.
An entry in the database tblspace points to
the database systables table.
Database tblspace
Tblspacessystables
Dbspace