Client software
Distributed Databases in practice
(Oracle and more )
• Overview
• Naming
• Database links
• Transparency
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Overview
Function distribution
Networking software (Net 8, since Oracle 8i)
Q
Q
Q
client server
server-server homogenous
server-server heterogenous
Gobal or local naming
Conversion of character sets, representation, data types
All kinds of networking tasks
Basic communication abstraction:
database link, unidirectional "pointer" to server
Proprietary protocol
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Client server
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Net 8 network layer
Protocol stack
Networking layer
-Naming
-Routing
-Session Mgment
- Transport
( as usual )
Different network protocols supported
figures adapted from Oracle slides
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Naming
Location Transparency … more or less
Every database has a global database name,
Oracle term: service name.
The global database name uniquely identifies each
database in the global network.
A global database:
database name (DB_NAME) and a hierarchical
domain name (DB_DOMAIN)
Unique <schema>.<relation> names
create public synonym sunStadt
for stadt@"sunseths.inf.fu-berlin.de";
select * from sunStadt ;
Distributed join:
select s.name, s1.einwohner
from mystaedte s, sunStadt s1
where s.name = s1.name
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Name resolution
Distributed Ingres
Central name server - or
Ingres: forerunner of
Postgres
(Stonebraker, UCB)
local files ("tsnames.ora")
Every Client or Server must have defined
the address of its partner
-> Tsnames.ora file on each system with client or server
software
SUNSETHS.INF.FU-BERLIN.DE =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST =
sunset.inf.fu-berlin.de)(PORT = 1521))
)
(CONNECT_DATA =
(SID = SUNSETHS)
(SERVER = DEDICATED)
)
)
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Database link
Ingres Star distribution
subsystem on top of
Ingres
still in use
Architecture
• Star schema defined by
export of schema information from local databases
• Application access through global ("Star") schema
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Ingres / Star
"Pointer to instance or schema
CREATE PUBLIC DATABASE LINK "SUNSETHS1.INF.FU-BERLIN.DE"
CONNECT
TO "SCHWEPPE"
// fixed schema "schweppe"
IDENTIFIED BY "***"
USING 'SUNSETHS'
• Global Schema
managed at one site
Ö central component of DDBS
• Schema level registration
register table table2 as link
with node = node_c,
database = dbloc_c1;
select * from stadt@"sunseths.inf.fu-berlin.de";
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