万历朝的房价和盐价
http://blog.sina.com.cn/s/blog_4865b35c0100833i.html

手头有一张房契，写的是万历十五年七月，安徽某居民许先生买到一别墅，该别墅占地5亩，有楼房3间，平房28间。

Features:

Oracle Flashback Query
Oracle Flashback Version Query
Oracle Flashback Transaction Query
Oracle Flashback Table
Oracle Flashback Drop
Oracle Flashback Database

A transaction in Oracle begins when the first executable SQL statement is encountered. An executable SQL statement is a SQL statement that generates calls to an instance, including DML and DDL statements.
When a transaction begins, Oracle assigns the transaction to an available undo tablespace to record the rollback entries for the new transaction.

The redo log buffer is a circular buffer in the SGA that holds information about changes made to the database. This information is stored in redo entries. Redo entries contain the information necessary to reconstruct, or redo, changes made to the database by INSERT, UPDATE, DELETE, CREATE, ALTER, or DROP operations. Redo entries are used for database recovery, if necessary.

■ Set the LOG_CHECKPOINT_TIMEOUT initialization parameter
■ Set the LOG_CHECKPOINT_INTERVAL initialization parameter
■ Set the FAST_START_MTTR_TARGET initialization parameter
■ Set the size of the smallest redo log

For information on which mechanism is controlling checkpointing behavior, query the V$INSTANCE_RECOVERY view.

偶然读到中科院计算所研究员、龙芯CPU首席设计师胡伟武接受采访的实录，才知道自己对“道高一尺，魔高一丈”这个成语错误理解了那么多年。一切都源于武侠小说的误导，那里，这个成语常被坏人用来形容正义不能战胜邪恶。

SELECT NAME, VALUE, DECODE (isdefault, 'TRUE', 'Y', 'N') AS "Default",
DECODE (isem, 'TRUE', 'Y', 'N') AS sesmod,
DECODE (isym,
'IMMEDIATE', 'I',
'DEFERRED', 'D',
'FALSE', 'N'
) AS sysmod,
DECODE (imod,
'MODIFIED', 'U',
'SYS_MODIFIED', 'S',

A bottleneck is quite literally a small part of your installation (hardware or software), where too much processing is being funneled through a specific area. In other words, far too much is going on in one particular area of an installation, in comparison with any other part.


SELECT a.event "Event", a.time_waited "Total Time", a.total_waits "Waits",
a.average_wait "Average", a.total_timeouts "Timeouts", b.wait_class
FROM v$system_event a, v$event_name b
WHERE a.event = b.NAME AND b.wait_class NOT IN ('Cluster', 'Idle')
ORDER BY a.event;


SELECT 'Latch Hit Ratio ' "Ratio",
ROUND ((SELECT SUM (gets) - SUM (misses)
FROM v$latch) / (SELECT SUM (gets)
FROM v$latch) * 100,
2
)
|| '%' "Percentage"
FROM DUAL;


SELECT a.NAME "Pool", a.physical_reads, a.db_block_gets, a.consistent_gets,
(SELECT ROUND ( ( 1
- (physical_reads
/ (db_block_gets + consistent_gets)
)
)
* 100
)
FROM v$buffer_pool_statistics


SELECT 'Short to Long Full Table Scans' "Ratio",
ROUND
( (SELECT SUM (VALUE)
FROM v$sysstat
WHERE NAME = 'table scans (short tables)')
/ (SELECT SUM (VALUE)
FROM v$sysstat
WHERE NAME IN
('table scans (short tables)',


SELECT 'Index to Table Ratio ' "Ratio",
ROUND ( (SELECT SUM (VALUE)
FROM v$sysstat
WHERE NAME LIKE 'index fast full%'
OR NAME = 'index fetch by key'
OR NAME = 'table fetch by rowid')
/ (SELECT SUM (VALUE)
FROM v$sysstat


SELECT 'Dictionary Cache Hit Ratio ' "Ratio",
ROUND ((1 - (SUM (getmisses) / SUM (gets))) * 100, 2)
|| '%' "Percentage"
FROM v$rowcache;



SELECT 'Library Lock Requests' "Ratio",
ROUND (AVG (gethitratio) * 100, 2) || '%' "Percentage"
FROM v$librarycache
UNION
SELECT 'Library Pin Requests' "Ratio",
ROUND (AVG (pinhitratio) * 100, 2) || '%' "Percentage"
FROM v$librarycache
UNION
SELECT 'Library I/O Reloads' "Ratio",
ROUND ((SUM (reloads) / SUM (pins)) * 100, 2) || '%' "Percentage"