今天周末，在家休息，好不容易闲来无事，来回串门，无意间发现隔壁口碑的室友，有一块挺精致的鼠标垫，细细一看，上面列了7个点：
1、 坚持不懈的向团队传达目标
2、 崇拜质量
3、 每天都和项目成员聊上两句
4、 敢于说不，慎于说不
5、 帮助项目成员解决困难，而不是帮他干活
6、 敏感，不将风险留到最后才面对
7、 懂得欢庆
由于和目前项目过程中出现的一些问题有惊人的相似，于是抄录下来，以供大家参考。尤其是3、5、6、7都是做为技术出身的一线管理者比较缺乏的。
原文在此：http://www.alisdn.com/wordpress/?p=1492
全文：ref:http://www.ruanyifeng.com/blog/2009/05/10_lessons_from_a_failed_startup_part_one.html
4. 珍惜每一分钟
Set a dollar value on your time.
我有一个坏习惯，那就是喜欢找便宜货，因此经常同别人砍价。为了把无线上网的账单降低100美元，我可以花上3个小时去谈判。我的错误在于忽略了时间的价值。相对于我们获得的投资，这样使用时间简直太不值得了。
时间比钱重要，因为你没法挣来更多的时间。（Time is arguably more valuable than money because you can’t raise more time.）
（【感谢】我太喜欢上面这句话了。很多人的失败，不是因为他没有能力，而是因为他无法有效地管理时间。我自己就是一个例子，一定要时刻鞭策自己提高效率啊。）
The kernel parameters and shell limits presented in this section are recommended values only as documented by Oracle. For production database systems, Oracle recommends that you tune these values to optimize the performance of the system.
On both Oracle RAC nodes, verify that the kernel parameters shown in this section are set to values greater than or equal to the recommended values. Also note that when setting the four semaphore values that all four values need to be entered on one line.
Setting Shared Memory
Shared memory allows processes to access common structures and data by placing them in a shared memory segment. This is the fastest form of inter-process communications (IPC) available, mainly due to the fact that no kernel involvement occurs when data is being passed between the processes. With shared memory, data does not need to be copied between processes.
Oracle makes use of shared memory for its Shared Global Area (SGA) which is an area of memory that is shared by all Oracle backup and foreground processes. Adequate sizing of the SGA is critical to Oracle performance because it is responsible for holding the database buffer cache, shared SQL, access paths, and so much more.
To determine all shared memory limits, use the following:
# ipcs -lm
------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 4194303
max total shared memory (kbytes) = 1073741824
min seg size (bytes) = 1
in My Env:
[oracle@crOracle01 ~]$ ipcs -lm
------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 67108864
max total shared memory (kbytes) = 17179869184
min seg size (bytes) = 1
Setting SHMMAX
The SHMMAX parameters defines the maximum size (in bytes) for a shared memory segment. The Oracle SGA is comprised of shared memory and it is possible that incorrectly setting SHMMAX could limit the size of the SGA. When setting SHMMAX, keep in mind that the size of the SGA should fit within one shared memory segment. An inadequate SHMMAX setting could result in the following:
ORA-27123: unable to attach to shared memory segmentFor most Linux systems, the default value for SHMMAX is 32MB. This size is often too small to configure the Oracle SGA. The default value for SHMMAX in Enterprise Linux 5.0 is 4GB. Note that this value of 4GB is not the "normal" default value for SHMMAX in a Linux environment — Oracle Enterprise Linux 5.0 inserts the following two entries in the file /etc/sysctl.conf:
..................................................................I highly recommend removing these two values from both Oracle RAC nodes and replacing them with the recommended values document by Oracle. All recommended Oracle kernel parameter values are documented in this section.
Oracle recommends sizing the SHMMAX parameter as the minimum of (4GB - 1 byte), or half the size of physical memory (in bytes), whichever is lower. Given my nodes are configured with 2GB of physical RAM, I will configure SHMMAX to 1GB:
# sysctl -w kernel.shmmax=1073741823
# echo "kernel.shmmax=1073741823" >> /etc/sysctl.conf
Setting SHMMNI
We now look at the SHMMNI parameters. This kernel parameter is used to set the maximum number of shared memory segments system wide. The default value for this parameter is 4096.
You can determine the value of SHMMNI by performing the following:
# cat /proc/sys/kernel/shmmni 4096 The default setting for SHMMNI should be adequate for your Oracle RAC 11g Release 1 installation.Setting SHMALL
Finally, we look at the SHMALL shared memory kernel parameter. This parameter controls the total amount of shared memory (in pages) that can be used at one time on the system. In short, the value of this parameter should always be at least:
ceil(SHMMAX/PAGE_SIZE)The default size of SHMALL is 2097152 and can be queried using the following command:
# cat /proc/sys/kernel/shmallThe default setting for SHMALL should be adequate for our Oracle RAC 11g Release 1 installation.
2097152
[oracle@crOracle01 ~]$ cat /proc/sys/kernel/shmall
4294967296
(Note: The page size in Red Hat Linux on the i386 platform is 4,096 bytes. You can, however, use bigpages which supports the configuration of larger memory page sizes.)
Setting Semaphores
Now that you have configured your shared memory settings, it is time to configure the semaphores. The best way to describe a "semaphore" is as a counter that is used to provide synchronization between processes (or threads within a process) for shared resources like shared memory. Semaphore sets are supported in UNIX System V where each one is a counting semaphore. When an application requests semaphores, it does so using "sets."
To determine all semaphore limits, use the following:
# ipcs -lsYou can also use the following command:
max number of arrays = 128
max semaphores per array = 250
max semaphores system wide = 32000
max ops per semop call = 32
semaphore max value = 32767
# cat /proc/sys/kernel/sem
250 32000 32 128
Setting SEMMSL
The SEMMSL kernel parameter is used to control the maximum number of semaphores per semaphore set.
Oracle recommends setting SEMMSL to the largest PROCESS instance parameter setting in the init.ora file for all databases on the Linux system plus 10. Also, Oracle recommends setting the SEMMSL to a value of no less than 100.
Setting SEMMNI
The SEMMNI kernel parameter is used to control the maximum number of semaphore sets in the entire Linux system. Oracle recommends setting the SEMMNI to a value of no less than 100.
Setting SEMMNS
The SEMMNS kernel parameter is used to control the maximum number of semaphores (not semaphore sets) in the entire Linux system.
Oracle recommends setting the SEMMNS to the sum of the PROCESSES instance parameter setting for each database on the system, adding the largest PROCESSES twice, and then finally adding 10 for each Oracle database on the system.
Use the following calculation to determine the maximum number of semaphores that can be allocated on a Linux system. It will be the lesser of:
SEMMNS -or- (SEMMSL * SEMMNI)Setting SEMOPM
The SEMOPM kernel parameter is used to control the number of semaphore operations that can be performed per semop system call.
The semop system call (function) provides the ability to do operations for multiple semaphores with one semop system call. A semaphore set can have the maximum number of SEMMSL semaphores per semaphore set and is therefore recommended to set SEMOPM equal to SEMMSL.
Oracle recommends setting the SEMOPM to a value of no less than 100.
Setting Semaphore Kernel Parameters
Finally, we see how to set all semaphore parameters using several methods. In the following, the only parameter I care about changing (raising) is SEMOPM. All other default settings should be sufficient for our example installation.
# sysctl -w kernel.sem="250 32000 100 128"
# echo "kernel.sem=250 32000 100 128" >> /etc/sysctl.conf
Setting File Handles
When configuring the Oracle RAC nodes, it is critical to ensure that the maximum number of file handles is sufficiently large. The setting for file handles denotes the number of open files that you can have on the Linux system.
Use the following command to determine the maximum number of file handles for the entire system:
# cat /proc/sys/fs/file-max
205733
[oracle@crOracle01 ~]$ cat /proc/sys/fs/file-max
248278
[oracle@oracle01 ~]$ cat /proc/sys/fs/file-max
6553600
Oracle recommends that the file handles for the entire system be set to at least 65536.
# sysctl -w fs.file-max=65536
# echo "fs.file-max=65536" >> /etc/sysctl.conf
The file-nr file displays three parameters: total allocated file handles, currently used file handles, and maximum file handles that can be allocated.
Note: If you need to increase the value in /proc/sys/fs/file-max, then make sure that the ulimit is set properly. Usually for 2.4 and 2.6 kernels it is set to unlimited. Verify the ulimit setting by issuing the ulimit command:
# ulimit unlimitedSetting IP Local Port Range
Configure the system to allow a local port range of 1024 through 65000.
Use the following command to determine the value of ip_local_port_range:
# cat /proc/sys/net/ipv4/ip_local_port_range
# sysctl -w net.ipv4.ip_local_port_range="1024 65000"
# echo "net.ipv4.ip_local_port_range = 1024 65000" >> /etc/sysctl.conf
Setting Shell Limits for the oracle User
To improve the performance of the software on Linux systems, Oracle recommends you increase the following shell limits for the oracle user:
| Shell Limit | Item in limits.conf | Hard Limit |
| Maximum number of open file descriptors | nofile | 65536 |
| Maximum number of processes available to a single user | nproc | 16384 |
To make these changes, run the following as root:
cat >> /etc/security/limits.conf <oracle soft nproc 2047
oracle hard nproc 16384
oracle soft nofile 1024
oracle hard nofile 65536
EOF
cat >> /etc/pam.d/login <# Added for Oracle Shell Limits
session required /lib/security/pam_limits.so
session required pam_limits.so
ref:http://www.oracle.com/technology/pub/articles/hunter_rac11gr1_iscsi_2.html
EOF
As root, make a file that will act as additional swap space, let's say about 500MB:
# dd if=/dev/zero of=tempswap bs=1k count=500000
Now we should change the file permissions:
# chmod 600 tempswap
ref: http://www.cyberciti.biz/tips/how-to-mount-iso-image-under-linux.html
An ISO image is an archive file (disk image) of an optical disc using a conventional ISO (International Organization for Standardization) format. ISO image files typically have a file extension of .ISO. The name "ISO" is taken from the ISO 9660 file system used with CD-ROM media, but an ISO image can also contain UDF file system because UDF is backward-compatible to ISO 9660.
You can mount an ISO images via the loop device under Linux. It is possible to specify transfer functions (for encryption/decryption or other purposes) using loop device.
But, how do you mount an ISO image under Linux? You need to use mount command as follows:
1) You must login as a root user, if not root user then switch to root user using following command:$ su -
2) Create the directory i.e. mount point:# mkdir -p /mnt/disk
3) Use mount command as follows to mount iso file called disk1.iso:# mount -o loop disk1.iso /mnt/disk
4) Change directory to list files stored inside an ISO image:# cd /mnt/disk
# ls -l
A loop device is a pseudo-device that makes a file accessible as a block device. Loop devices are often used for CD ISO images and floppy disc images. Mounting a file containing a filesystem via such a loop mount makes the files within that filesystem accessible. They appear in the mount point directory using above commands.
我的实验：
[root@CRRACTEST media]# vi mnt.sh
mount -o loop Enterprise-R5-U2-Server-x86_64-disc1.iso /media/disk1
mount -o loop Enterprise-R5-U2-Server-x86_64-disc2.iso /media/disk2
mount -o loop Enterprise-R5-U2-Server-x86_64-disc3.iso /media/disk3
mount -o loop Enterprise-R5-U2-Server-x86_64-disc4.iso /media/disk4
记录一下：）
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