Oracle ASM:

    As per my knowledge oracle will dominates everything.  May be, if you have another opinion also but after reading this article you will definitely change your option.  From 10g on words, the most beautiful concept was introduced by oracle i.e Oracle grid Infrastructure. Why this concept was came into picture? Why we are moving with ASM? What is the advantages we had with this?

1) why this concept came into picture?

A:  before 10g, we had data guard concepts for availability and RMAN is helpful for cloning database and recovery’s but we doesn't have an alternative for providing the performance and security. Performance is majorly depends on I) I/O ii) CPU iii) memory.

• CPU is totally depends on the requirement and hardware availability.
• Memory is just as RAM If we had well size for the I/O operations automatically the application performance is good.
• I/O is playing a virtual role to improve the performance. Mostly each and every database is used to make the transaction as DML operations, fetching the data from the data files and updating new data. It takes the place to decide the application whether performance is goes down or up. How the I/O operation done and how it will impact the total applica  tion. How oracle is providing the performance for a application which is tightly embedded with hardware? Here you have look about I/O's history.

Database creation is done in 3 different ways.

1) Db creation with File system:

Based on the user necessity, we can store CRD files into different location. We can provide the multiplexing with multiple user locations.

Advantages:

• user locations never contains traffic ,so automatically I/O’s  are increased.
• performance proved. No traffic means definitely we can reach home safely and quickly.

Disadvantages:

• if the file system buffer was very small to fetch the data from multiple locations. It will improves the traffic for transferring data and as well as I/O are increased means it will degrades the OS performance. So everything goes done. Better to shift.

2) OMF :

Oracle managed file system is very simple strategy was give by oracle. Oracle took the responsibility about storing the CRD files locations.

Advantages:

•  easier to use because we don't bother about locations and no need to remember the file location
• rare chances  to a DBA  for a mistake while storing or creating a new CRD files.
• automatically oracle is handling it.

Disadvantages:

• if your application was built on OMF there is chances to lose the performance because oracle will store the CRD files in one location. Fetching the data from one location means IO are increased so definitely performance goes down.

3) Raw device: up to the mark we never provide the performance to  a application. Per suppose we are using raw devices means we will definitely and freely synchronized with performance. Because we are directly fetching the data from raw device. And we can using multiple disks for multiple files. It drastically improved the performance. In a manner of less traffic and more I/O's.

Advantages:

• performance is high, reason is fetch the data from physical device is very fast and no file system for a disk.

Disadvantages:

•  one file for one disk means there is chance to so much disk space wastage for storing small files as control file,spfile,pfile,redo files
•  no chance to store the redo files because in raw devices we cant store two files in a single disk or partition.

2) Why we are moving with ASM?

 In Linux there is a concept is available for maintaining the raw devices. It will generates the file system for raw devices and it will helpful to maintain the multiple files in a single raw device. It shows the perfect space utilization for raw devices i.e. logical volumes. It is simply act as tablespace. Tablespace is a logical exposer to interact with a datafile. In a same way logical volumes are available and taking care about raw devices to meet our requirements. The logical volumes are providing a logical file system. Some basic commands are working for user flexibility. We can make the partition on a single disk into multiple raw devices. This LVM feature was newly established from Linux but in Oracle we doesn't have this feature up to 10g. ORACLE has a strategy and always maintaining it when we are in a compilation be like a hero. No one can touch us. Then oracle introduce the concept with ASM to handle the disk group same as LVM. After this oracle DBA as handle to the Linux administration work with the help of ASM concept.  Not for domination, just to do the justification for the client.

3) What are the advantages we had with ASM?

• Working with Raw devices means automatically application performance is increased.
• ASM  stripping gives us better performance, mirroring gives us availability
• No need of 3^rd party software. Grid infrastructure also freely available with RDBMS.
• ASM built on top of OMF for the file convenient.
• Automatically I/O load balancing with ASM.
•  Disk Redundancy is available in different modes
• SPAM properties are simply followed by ASM.. p-performance, a-availability, m-manageability.