MIDAS中事务并发的问题(200分)

T

tonglifeng

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• 2000-01-24

• #1

我做了一个APP SERVER，工程其中有一个主FORM（上面有TDATABASE构件）
若干个TRemoteDatamodule（里面的QUERY等的DATABASE属性指向FORM中的DATABASE），TRemoteDatamodule为miMultiInstance,有个过程如SAVE（在一个事务中存取多个表SQLSERVER6.5）供客户端调用，应用中发现，当出现事务并发时，报 a user transaction already in progress错误，请问，我的问题出在哪里？代码结构如下：
database1.starttransaction
try
provider1.apply...
provider2.apply...
database1.commit
except
database1.rollback
end;

 

G

g622

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• 2000-01-25

• #2

为什么不把TDATABASE构件放在TRemoteDatamodule中。

 

C

Crane

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• 2000-01-26

• #3

to g622:
有关系吗?

 

S

subseven

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• 2000-01-26

• #4

听听

 

X

xWolf

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• 2000-01-26

• #5

TProvider creates a transaction for the update operation
---------------------
and then
calls the ApplyUpdates method of its Resolver component.
去掉你写的Database.StartTransaction

 

G

g622

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• 2000-01-26

• #6

to crane: 只是奇怪。
agree xwolf

 

C

Crane

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• 2000-01-26

• #7

to xWolf:
这怎么行,人家是要把几个provider当作同一事务!

 

T

tonglifeng

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• 2000-01-26

• #8

据说把DATABASE放在REMOTEDATAMODULE中，并放入一个SESSION构件，设置其
AUTOSESSIONNAME为TRUE，可以解决，但若把DATABASE。KEEPCONNECT：=TRUE
会不会浪费SQLSERVER的连接数量，从而影响其性能？

 

T

tonglifeng

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• 2000-01-26

• #9

我还有个问题请教各位，我有个程序（MIDAS客户端DELPHI5）如果把某个窗体打开
在编译，则退出DELPHI时报地址错，若不打开则正常，若打开——编译——CLOSE这个UNIT——退出则也正常。不知是什么问题

 

L

Liuz

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• 2000-01-29

• #10

the key is where did u put the implementation of "save" method under
the option miMultiInstance.
i guess that u published the "save" method thru remotedatamodule to
client. u should code the method like following:
on remotedatamodule:
procedure Save(...);
begin
//call the implementation code on another unit (here is Form1)
do
Save(...);
end;

on Form1
proceduredo
Save(...)
begin
database1.starttransaction
try
provider1.apply...
provider2.apply...
database1.commit;
except
database1.rollback;
end;
end;

 

B

Bianyueliang

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• 2000-01-29

• #11

通过DCOM调用Application Server时,Tthreading Modal是对TRemoteDatamodule而言，Main Form应该在默认Thread中运行。当多台客户机同时运行同一个Server时，就有对应个数的TRemoteDatamodule对象被启动。
DATABASE放在TRemoteDatamodule中并不影响同一事务处理，SESSION构件是需要的。

 

孙

孙立

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• 2000-02-01

• #12

在这种情况下,Inprise不推荐自己使用事务,应该用ApplyUpdates自动处理事务.
实际上,数据库操纵只要2种:
1.单据录入.不论单表还是主从表,用ApplyUpdates都没问题.
2.转帐类.不要用Delphi做,用存储过程做.

 

T

tonglifeng

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• 2000-02-08

• #13

to liuz:
请问：DOSAVE放在哪里有什么不同?

 

L

Liuz

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• 2000-02-10

• #14

App server is a multi-thread program. each remotedatamodule is in its
own thread. u put tdatabase in main form, every rmd invoke it from own
thread. this condition like that serval threads invoke the same
resource outside.
for instance:
user A begin
to save using your original routine. now TDatabase is in
a transaction. because of multi-thread, during A saving the data,
another user B can begin
to save also, then
your routine requests
TDatabase in main form to begin
another transaction. so the error
"a user transaction already in progress" happened.
how to solve:
one way is like i told u last time to modify save routine, make multi-
thread into single thread when saving data.
another way is that put TDatabase component in remotedatamodule and
set HandleShared = True. let each thread own his database session.
this way is recommended strongly.

 

T

tonglifeng

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• 2000-02-10

• #15

TO LIUZ:
这么做过吗？

 

W

wen

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• 2000-02-10

• #16

提供以下几點相關意見,供參考:
1 N_Tier開發中要求把數据連接控件放在server端,Tdatabase一般要放在RemoteDatamodule中,設HandleShared = True.
2 applyupdate() 執行時自動啟動一個事務,在這個事務中可以保証數据的一致性.
3 在前端与后端協同完成一個事務:用一個variant型變量傳遞要保存的多個數据集(delta)到后端再啟動事務.
...

 

L

LeeChange

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• 2000-02-10

• #17

台湾的李维教过一招,但现在不记得了,回家看看书再来告诉你.

 

L

Liuz

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• 2000-02-11

• #18

of course. i have been engaged in developping Midas application for
about tow years.do
u try it.do
es it work?
welcome further question.

 

X

xyzer

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• 2000-02-20

• #19

Database不支持嵌套事务，因此将Database放在Form中就使多个
RemoteDatamodule共用了同一个Database,当再次启动事务时便会
出错。
将Database放在RemoteDatamodule中，这样每个RemoteDatamodule
都使用的是独立的Database，就可避免错误出现。

 

S

souledge

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• 2000-07-05

• #20

使用session组件，并设置其AutoSessionName属性为True，否则所有的用户都使用
同一个默认的session，肯定会有影响。