Database Reference
In-Depth Information
SQL (Structured Query Language)
SQL is a computer language designed for the retrieval and management of data in relational
database management systems . Among its features are creation, modification, and removal
of database schema objects (DDL), data manipulation (DML), and database object access
control management.
SQL trace file, extended
An extended SQL trace file contains a log of the actions of one or more database clients.
Actions include parse , execute , and fetch . The trace levels 1, 4, 8, and 12 control the amount
of detail in SQL trace files.
Scalability
Scalability is a desirable property of a system, network, or application program, which indi-
cates its ability to either handle growing workloads in a graceful manner, or to be readily
enlarged.
Sleeping
Processes may be put to sleep when a requested resource is not available. Sleeping processes do
not consume CPU time. Thus sleeping is preferred over polling .
Swapping
Transfer of process virtual memory from RAM to disk.
System Global Area (SGA)
Memory structure containing the database buffer cache, the shared pool, java pool, large
pool, Streams pool, and the log buffer. On UNIX, the SGA resides in shared memory.
System Change Number
Each modification of data in an ORACLE database is stamped with a monotonically increasing
number, the System Change Number . Backup, recovery, and consistent read are implemented
based on the System Change Number.
System call
A routine at the interface between an operating system and user-level programs that run
under control of the operating system. System calls execute in kernel mode, whereas appli-
cation code executes in user mode. Access to devices, such as disks and network adapters, is
implemented with system calls. UNIX system calls are standardized by the POSIX standard.
Search WWH ::




Custom Search