Database Reference
In-Depth Information
APPENDIX C
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Glossary
Application instrumentation
Instrumentation
is the ability of software to measure its own performance. An instrumented
ORACLE application passes module, action, and client identifier to the DBMS, allowing a
DBA to collect metrics based on this information.
Concurrency
Concurrency
is a property of computer systems that have the capability to execute multiple
processes at the same time. Concurrent processes may interact with each other through
interprocess communication.
Connect string
A
connect string
consists of a user name, password, and optionally a
Net service name
or
other specification for contacting an Oracle Net Services TNS Listener, for example
ndebes/
Connection pool
A
connection pool
is a set of database connections, which is usually maintained by an appli-
cation server. Connections to an ORACLE instance are opened when the connection pool is
initialized and remain open for the lifetime of the connection pool or until an idle timeout
expires. Clients of the connection pool, for example Java Beans, request a connection, run
some SQL statements, and return the connection to the pool. Connection pooling removes
the overhead of establishing a new database session for each request.
Consistent read
A
consistent read
is a snapshot of data in the database based on the System Change Number,
which was current at the point in time when a SQL statement was initiated. If the data accessed
by the query has changed since the cursor was opened, the old values will be reconstructed
from undo segments in an undo tablespace.
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