Performance view V $ beginning
System Information V $ SYSTEM_EVENT is waiting for resources
V $ SESSION_EVENT session cumulative incidence of waiting for an event
Detailed time V $ SESSION_WAIT session is waiting or have to wait for information
V $ SESSION is waiting or have to wait for the information session
V $ METRICNAME view the cache hit rate
Oracle Database IO planning principles:
1 using the disk staging techniques IO dispersed in a plurality of axes
Table 2 using the spatial direct isolation and positioning of various types of IO
The redo log and its mirror 3 is placed on the least busy two devices
The overhead 4 is uniformly allocated to the available disk drives
5 archive and redo log files on different devices
RAID inexpensive (independent) disk redundant array
RAID-0 does not have a redundant disk array
Full copies of RAID-1 data
RAID-0 + 1 combines RAID-1-one mapping of disk and RAID-0 column
Provides redundancy RAID-3 parity information stored on a single disk array.
RAID-5 using the parity information to provide redundancy, but distributed saving
A huge database VLDB
Global program to program global area PGA
Parallel Database: Block - a parallel range, based on the partition parallel
Specify the size of the SGA or other shared pool at initialization, once the instance is running, you can not change.
oracle using SGA:
One pair of tables and the data block index data cache, and placed in the database cache
Two pairs are parsed and optimized SQL statements, stored procedures and data dictionary information is cached, and placed in shared memory pool
3 log information is written to disk money in the log buffer cache
Database Cache:
Hits: request from the cache to the percentage of the data block from the data block request to the disk. (If the hit rate is below 90%, the performance can be improved to increase initialization DB_CACHE_SIZE)
Shared memory pool:
Storage needed to send SQL statements to the database and execute SQL statements data dictionary information
redo log buffer:
After a transaction is committed or when the log buffer is filled one-third of the time. , The log cache will be written to disk log file.
Query Result Cache:
By avoiding disk read operation and a cache block index;
Repeat the process by caching parsed and optimized SQL statements
Oracle uses PGA:
1 content storage server process for temporary variables, etc.
SQL information storage memory 2 is executed
3 As part of the record sort of SQL execution memory occupied
timesTen memory database acquisition operation by reducing latency in turn provides the best performance database
Reproduced in: https: //my.oschina.net/u/204616/blog/545005