2008年3月26日
Ubuntu is not an official supported linux version from Oracle, so I still get some errors during the install process even with required configuration, anyway, it can work and what i'm doing here is try to setup an experiment environment, it's enough to me, any one who want to deploy Oracle in product mode should have supported linux platform like RedHat, OK, following is the steps i have to install it:
1. If you were in multihomed enviroment, set the ORACLE_HOSTNAME variable:
export ORACLE_HOSTNAME=machine_name.domain_name
2. Create create OSDBA (dba) group, Oracle Inventory group (oinstall) and a user "oracle" which has "dba" as its login group and oinstall as its 2nd group.
3. Modify /etc/sysctl.conf, set kernel parameter:
kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
fs.file-max = 65536
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 1048576
net.core.rmem_max = 1048576
net.core.wmem_default = 262144
net.core.wmem_max = 262144
4. Modify /etc/security/limits.conf to improve the "number of process" and "number of open file" performance for oracle:
oracle soft nproc 2047
oracle hard nproc 16384
oracle soft nofile 1024
oracle hard nofile 65536
5. Modify /etc/pam.d/login, add:
session required /lib/security/pam_limits.so
session required pam_limits.so
6. Modify /etc/profile:
if [ $USER = "oracle" ]; then
if [ $SHELL = "/bin/ksh" ]; then
ulimit -p 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
fi
7. Change user to oracle if you haven't done it yet
8. Create base directory, for me it's "/app/oracle"
9. Export ORACLE_BASE, ORACLE_SID
export ORACLE_BASE=/app/oracle
export ORACLE_SID=orcl
10. If you're trying to install oracle with a X window:
DISPLAY=your.ip.address:0.0 ; export DISPLAY
11. run installer:
./runInstaller
12. Oracle should start, if the installer GUI cannot be start, check the error messages, most time it's because a wrong X window configuration, if you are running X window with Xming, just like me, please do make sure to check the "No Access Control" check box in the launch, otherwise, Xming will reject the connection.
13. Now the GUI shoudl open, like what you did in the Windows system, fullfill required value and click next, ingore all errors if there is any condition that is not match, click finish in the last step, it should start install process.
14. After install oracle, the installer GUI will ask you to run two .sh files, run it with a root role.
15. You can try to visit
https://you.ip.address:1158/em to see is that OK for you.
16. How to start oracle:
export ORACLE_BASE=/app/oracle
export ORACLE_HOME=/app/oracle/product/11.2.0/dbhome_1
export ORACLE_OWNR=oracle
export ORACLE_SID=orcl
export PATH=$PATH:$ORACLE_HOME/bin
lsnrctl start
sqlplus /nolog
connect /as sysdba
startup
quit
emctl start dbconsole
Reference
http://download.oracle.com/docs/cd/B19306_01/install.102/b15660/pre_install.htm#BABDFJAE
1. Type command: lsusb
Bus 002 Device 003: ID 19d2:fff5 ONDA Communication S.p.A.
2. Install "usb-modeswitch", then re-plugin modem again and input command "lsusb" again, you should get the following output
Bus 002 Device 003: ID 19d2:fff1 ONDA Communication S.p.A.
3. Notice in step #2, the product code has been changed from "fff5" to "fff1".
4. Install package "wvdial" which is used to dail up
5. Type command: "sudo modprobe usbserial vendor=0x19d2 product=0xfff1", don't forget the "sudo"
6. Type command: "sudo wvdialconf", again don't forget the "sudo", this will detect your modem
7. Modify file "/etc/wvdial.conf", following is what I have:
[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = Analog Modem
ISDN = 0
New PPPD = 1
Phone = #777
Modem = /dev/ttyUSB0
Username = yourName
Password = yourPassword
Baud = 921600
Stupid Mode = 1
Tonline = 0
8. Repeat step #5 again and then if you with not bad luck type in command "sudo wvdial", you should connect in.
9. If bad luck with you, click right-upper corner, there is a connection configuration menu, you can create "Mobile Broadband" connection yourself here, don't forget input the phone number "#777" (for China Telcom) and your username password, after that click connect, this works for me.
10. Good luck with you.
11. BTW, if it still cannot work, try to re-plug in the modem.
1. It will not get data from DB when just open the cursor, data will be loaded as an ongoing basis.
2. SCN: System Change Number/System Commit Number
3. FLASH BACK AS OF SCN;
4. You can also flash back table: FLASHBACK TABLE SOME_TABLE TO SCN :SCN_NUM;
5. But before you do a flash back operation on a table, do make sure you have already enbale ROW MOVEMENT on that table.
1. Do use oracle "Bind variable", it can increase the speed by 90 percent in 10g release1.
2. Understand how to use "lock", read never block write, vice verse.
3. There is a side effect from oracle regarding to the "lock", if you do want to control the access to one row at a specify time (like doing an if 'this row belong to some search condition' then 'modify this row' action), you have to write some logic yourself, for example use the "for update" statement, like: "select * from x where x.id = 1 for update", so that you can lock the row only with id equals to '1' and then modify this row, so that some orther concurrence requests should execute the same sql first, yes, with the same 'for update' statement, and because you already have locked this row(id = 1), orther requests cannot get the access to it, and you get the access control to this row.
4. Regardint to item 3, it will not decrease the concurrence level, because first you only lock the item with id equals to 1 and there maybe thousands of items in your table, second, it will not block the read request.
這該死的問題讓我竟然沒有想到解決方案...腦子生銹了？呵呵，算了...
該問題最經典的解答，簡直是一句話驚醒夢中人啊
“用兩個指針，一個的步長為 1，另外一個的為 2，從表頭開始一起往前走，如果相遇，表明有環路，否則就是沒有了。”
下來，不用說什么了吧，用JAVA實現的話，聲明兩個Iterator A 和 B，A 每次調用兩個NEXT，B只調用一次，如果他們能夠相遇，就是有環...我操
The first is about identity generator, this is something I ingored and find really interesting later when I read back the document.
When you choose "native" (for plain
hibernate) or "AUTO" (for JPA which use
hibernate as provider) as identity generator, it (actually they are the same identity generator but with different name in different scope) will pick other identity generators like identity, sequence, or hilo, depending on the capabilities of the underlying database. Use this generator to keep your mapping metadata portable to different database management systems.
If your underlying DB is oracle, it will automatically create a sequence for you which means choose the sequence as identity generator, that's really interesting, at least for me for the first time when it comes to me.
The second is about the flush and close session operations when to use hibernate with JTA transaction.
You should manually flush your operation by call flush method and close your session by calling close method when you try to use JTA transaction instead of
hibernate Transaction API, these is because
hibernate Transaction API does thoes operations automatically for you. But, with following configuration, it can also be done automatically for you by
hibernate, though you are still with JTA transaction.
hibernate.transaction.flush_before_completion=true
hibernate.transaction.auto_close_session=true
The third is about an interesting code snatch listed as follow:
1 Session session = sessionFactory.openSession();
2 session.beginTransaction();
3 session.save(new Item());
4 session.close();
What happen if you don't commit the transaction? It's depends on the underlying DB, for oracle it will commit any uncommited transactions, but for many other DB vendors, they will roll back any pending transactions.
Timer service in EJB3 with anotation is fairly simple, I give you an example as follow, and it's really simple and self-explanation:
1 package com.ramon.expejb3.session.impl;
2
3 import javax.annotation.Resource;
4 import javax.ejb.Stateless;
5 import javax.ejb.Timeout;
6 import javax.ejb.Timer;
7 import javax.ejb.TimerService;
8
9 import com.ramon.expejb3.session.Greeting;
10
11 @Stateless(name = "Greeting")
12 public class GreetingBean implements Greeting {
13
14 @Resource
15 TimerService ts;
16
17 /* (non-Javadoc)
18 * @see com.ramon.expejb3.session.Greeting#greeting(java.lang.String)
19 */
20 public void greeting(String name) {
21 System.out.println("Hello " + name + ".");
22 ts.createTimer(1 * 1000, 5 * 1000, name);
23 System.out.println("Create timer for " + name + ".");
24 }
25
26 @Timeout
27 public void timeout(Timer timer) {
28 String name = (String)timer.getInfo();
29 System.out.println(name + " TIME OUT.");
30 //timer.cancel();
31 }
32 }
33
It's the "
GreetingBean" I introduced in part one of this series article with TimerService injected,
@Resource anotation inject the time service we want, it's totally free which is supported by the J2EE container that means we do not need any further steps to get the powerful schedule service. In the line 22, I crate a new timer, I think this could be more fit if it was called Task instead, there are several "createTimer" methods with different parameters, the one I used here describe the task should be execute 1 second delay and every 5 second one time in the future, the third parameter can be anything you want to pass in to the task, it can be get back use method Timer.getInfo() like line 28 does here.
Another important anotation here is the @Timeout anotation, this anotation tell container which method will be called when timeout for this task to be executed, you can only specify one timeout method for each Bean, if there is no @Timeout anotation at all, you will get some exception like "No timeout method specified" in Jboss server. Something funny here is that you should mark the timeout method as "public", otherwise, you will get the same error as no timeout method does, I do NOT think it's necessary, because the time out method should only be called by the container, "private" signature is enought for that, with "private" signature container still has the right to access this method with java reflection, nevertheless timer service in EJB3 is still a good tools for use.
I summarize what good/bad for timer service in EJB3 as follow:
Good news:
- It's free, it's supported by the EJB container.
- It's portable, it's supported by the EJB container as specified in EJB3 specification.
- It's easy to use, no need to learn more.
Bad news:
- The feature of EJB3 timer sevice is not as powerful as some third party timer service such as Quartz, but it's enough with EJB3 for ordinary daily job.
- There is no UI for you to monitor the timer you created.