異常：
Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: localhost:1521:orcl
Hibernate operation: Cannot open connection; uncategorized SQLException for SQL [???]; SQL state [null]; error code [0]; Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: localhost:1521:orcl ; nested exception is java.sql.SQLException: Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: localhost:1521:orcl


[quote]查詢數(shù)據(jù)庫當(dāng)前進(jìn)程的連接數(shù)：

　select count(*) from v$process;

　　查看數(shù)據(jù)庫當(dāng)前會(huì)話的連接數(shù)：

　　elect count(*) from v$session;

　　查看數(shù)據(jù)庫的并發(fā)連接數(shù)：

　　select count(*) from v$session where status='ACTIVE';

　　查看當(dāng)前數(shù)據(jù)庫建立的會(huì)話情況：

　　select sid,serial#,username,program,machine,status from v$session;

　　查詢數(shù)據(jù)庫允許的最大連接數(shù)：

　　select value from v$parameter where name = 'processes';

　　或者：show parameter processes;

　　修改數(shù)據(jù)庫允許的最大連接數(shù)：

　　alter system set processes = 300 scope = spfile;

　　(需要重啟數(shù)據(jù)庫才能實(shí)現(xiàn)連接數(shù)的修改)

　　重啟數(shù)據(jù)庫：

　　shutdown immediate;

　　startup;

　　查看當(dāng)前有哪些用戶正在使用數(shù)據(jù)：

　　select osuser,a.username,cpu_time/executions/1000000's' ,sql_fulltext,machine

　　from v$session a,v$sqlarea b

　　where a.sql_address = b.address

　　order by cpu_time/executions desc;

　　備注：UNIX 1個(gè)用戶session對(duì)應(yīng)一個(gè)操作系統(tǒng)process，而Windows體現(xiàn)在線程。

　　啟動(dòng)oracle

　　su - oracle

　　sqlplus system/pwd as sysdba //進(jìn)入sql

　　startup //啟動(dòng)數(shù)據(jù)庫

　　lsnrctl start //啟動(dòng)監(jiān)聽

　　sqlplus "/as sysdba"

　　shutdown immediate;

　　startup mount;

　　alter database open;

--

web應(yīng)用連接oracle數(shù)據(jù)庫時(shí)，經(jīng)常在查詢數(shù)據(jù)時(shí)發(fā)生

Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: 127.0.0.1:1521:ORCL

這種錯(cuò)誤，網(wǎng)上查了很多，都說是ip地址改變之后的問題，要把tnsnames.ora中的實(shí)例配置中改為計(jì)算機(jī)名，我試過之后問題還是不能解決，今天終于找到問題所在了，是數(shù)據(jù)庫連接數(shù)量的問題，12519錯(cuò)誤為監(jiān)聽不能提供服務(wù)，通常為數(shù)據(jù)庫進(jìn)程達(dá)到上限導(dǎo)致。

可以先執(zhí)行下 select count(*) from v$process ，看下現(xiàn)在系統(tǒng)有多少連接數(shù)，然后再查詢 select value from v$parameter where name = 'processes' ，看下oracle設(shè)置中設(shè)置了多少連接數(shù)，一般一個(gè)應(yīng)用都會(huì)使用20個(gè)，所以如果你開了幾個(gè)應(yīng)用的話（web、pl/sql、……）就會(huì)出這個(gè)問題了，這時(shí)只需要執(zhí)行下

alter system set processes = 300 scope = spfile;[/quote]

就可以了，當(dāng)然300可以根據(jù)實(shí)際情況設(shè)置。

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