请教各位高手：在多线程里面能否建立数据库连接

Question

我在主线程里面建立了数据库连接，在每个子线程里面实现数据库操作（PROC）,但子线程数目大于2时就会CORE，如果只有一个子线程则运行正常，实在不明白什么道理，我在子线程里面使用了事务控制语句，不知道是否如此使用会造成冲突？各位能否给点建议。

Answer 1

要在数据库操作前加锁
pthread_mutex_t     m_Mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock
.....
然后pthread_mutex_unlock

Answer 2

下午研究了一下发现PRO*C对线程有特定的用法，就是为每个线程申请一个特定的上下文，但我在编译时还是遇到了问题，如下:
sql_context ctx1;
EXEC SQL ENABLE THREADS;
EXEC SQL CONTEXT ALLOCATE :ctx1;
第三句话编译不通过，报错如下：
Semantic error at line 378, column 29, file autonextdealfork.pc:
        EXEC SQL CONTEXT ALLOCATE :ctx1;
我在编译选项中已经添加了trh\

Answer 3

如下是我的编译命令，已经添加了THREADS=YES的编译选项
proc threads=yes oraca=yes code=cpp dbms=v8 parse=partial sqlcheck=semantics \
                 userid=test/test@HP01 \
                 include=/usr/include \
                 include=/opt/aCC \
                 include=/opt/aCC/include \
                 include=/opt/aCC/include/iostream \
                 include=/opt/aCC/include/SC \
                 include=/oracle/precomp/public \
                 include=/oracle/rdbms/demo \
                 include=../include \
                 iname=autonextdealfork.pc oname=autonextdealfork.c

Answer 4

/*例子程序thread5.pc*/
#include <stdio.h>;
#include <stdlib.h>;
#include <string.h>;
#include <sqlca.h>;
#include <pthread.h>;

//主函数
int main()
{
        sql_context ctx1;
        EXEC SQL ENABLE THREADS;
        EXEC SQL CONTEXT ALLOCATE :ctx1;
        EXEC SQL CONTEXT USE :ctx1;
        int i=0;
        while(i<10)
        {
               
                printf("test %d",i);
                i++;
                sleep(atoi(sleepseconds));

        }
        EXEC SQL CONTEXT FREE :ctx1;
}
/*以下为编译语句*/
/*
proc threads=yes oraca=yes code=cpp dbms=v8 parse=partial sqlcheck=semantics \
                 userid=test/test@hp01 \
                 include=/usr/include \
                 include=/opt/aCC \
                 include=/opt/aCC/include \
                 include=/opt/aCC/include/iostream \
                 include=/opt/aCC/include/SC \
                 include=/oracle/precomp/public \
                 include=/oracle/rdbms/demo \
                 include=../include \
                 iname=thread5.pc oname=thread5.c
*/

以下为编译错误信息：
System default option values taken from: /oracle/precomp/admin/pcscfg.cfg

Semantic error at line 12, column 29, file thread5.pc:
        EXEC SQL CONTEXT ALLOCATE :ctx1;
............................1
PCC-S-02322, found undefined identifier
Semantic error at line 12, column 29, file thread5.pc:
        EXEC SQL CONTEXT ALLOCATE :ctx1;
............................1
PCC-S-02336, host variable expression has invalid type
Semantic error at line 12, column 29, file thread5.pc:
        EXEC SQL CONTEXT ALLOCATE :ctx1;
............................1
PCC-S-02391, Runtime context variable not of correct type
Semantic error at line 23, column 25, file thread5.pc:
        EXEC SQL CONTEXT FREE :ctx1;
........................1
PCC-S-02322, found undefined identifier
Semantic error at line 23, column 25, file thread5.pc:
        EXEC SQL CONTEXT FREE :ctx1;
........................1
PCC-S-02336, host variable expression has invalid type
Semantic error at line 23, column 25, file thread5.pc:
        EXEC SQL CONTEXT FREE :ctx1;
........................1
PCC-S-02391, Runtime context variable not of correct type

Answer 5

试试:
EXEC SQL  BEGIN DECALRE SECTION;
     sql_context ctx1;
EXEC SQL END  DECLARE SECTION;