Detailed explanation of the ocp dba ticket (zt)

I finally completed all the OCP DBA courses. Tired! In general, Oracle certification is worth the test. I have a ccnp and MCSE certificate, but after passing the DBA examination, I feel that I have not only deepened my understanding of modern databases, but also enriched the knowledge structure of computer science. In my opinion, Oracle databases even have some operating system functions.

There are quite a few things to remember about Oracle exams. The exam requirements are basically based on the original command line method, rather than graphical interface operations. Therefore, the table name, many of the corresponding scripts need to be remembered. For the whole DBA examination, there are hundreds of tables mentioned in the book, I think this is mainly because Oracle used to run on UNIX systems in the past, and there were not many graphic interface software available! This also increases the difficulty of the exam! The entire exam focuses on understanding concepts and not taking too many details. I think this is the case for foreign exams! For example, why is lock contention? However, the concept of Oracle is varied and countless!

The first SQL is the foundation. This is not difficult. As long as you practice multiple points on the machine, it is generally okay, but many concepts of PL/SQL, such as triggers, need to be clarified. If you have the foundation for database development, this course is just a piece of cake!

The second step is database management. It is an oracle Basic course and a core course. It mentions many concepts and methods that will be used repeatedly in future courses. For example, instance and corresponding processes (pmon, SMON, arc0, dbw0, etc ). The physical structure of a database consists of DBF Files, control files, redo log files, and archive files. The logic of the database consists of tablespace, segment, extent, block, and so on. You need to understand the basic operation process of Oracle. Oracle reads the parameter file settings to construct an instance in physical memory, and writes data in the database buffer of SGA to datafile on a regular or irregular basis through the dbwr process, at the same time, the SQL commands are also recorded by the lgwr PROCESS IN THE redolog file. The system regularly copies the redolog file into the archive file. The system provides rollback segment for the needs of transactional, this ensures read consistence.

The concept of this course is quite a lot, and it makes people think that the concept of Oracle storage is quite fine. For example, the segment block is divided into pctfree and pctuse, and the concept of row migrate and row chain is also mentioned by the way, it can be seen that Oracle's management of logical and physical objects can be very meticulous! In addition, SCN is not only stored in the control file, but also in the datafile header. The SCN is introduced to ensure the coordination and connection between various files in the system. There are too many optional parameters for many commands in this course! These parameters are described in detail in performance adjustment! You only need to remember the most basic statements!

Step 3: backup and recovery. If you have an understanding of operating system backup and recovery, it will be helpful. However, the difficulty in Oracle backup and recovery lies in the operations on logical objects, for example, the Import and Export commands can be used for table operations. RMAN is the focus. Oracle has many categories of backup and recovery, including archivelog and noarchivelog, full backup and incomplete backup, backup of read-only tablespace, and media recovery. It can be seen that Oracle backup is much more complicated than operating system backup!

In network management, the most practical application is the net8 setting and listener setting. There are still many commands used in this course, such as lsnctr, connection manger (CMAN), and namesctl. Oracle also made a set of protocol stacks corresponding to the OSI 7-layer network structure. I think OSI has its own network structure, and Cisco also made a set of network structures, now I find that Oracle is similar. I think it is ridiculous. I feel that OSI is only used for reference and has not been adopted by large manufacturers. I found that Oracle products are quite well-developed. the wonderful thing is that its intermediate layer structure integrates the router functionality and can convert the network protocol of Oracle services, and connection concentration is quite reasonable. Oracle makes a name server component equivalent to DNS server, which is similar to Microsoft DNS server. In terms of Network Security Authorization and authentication, I found that Cisco is very similar to Oracle, for example, both sides have Kerberos, radius and other authentication applications.

If you have knowledge about routing and operating system networks, this is quite simple! That is to say, people who have passed Cisco and Microsoft certification will be much more difficult!
In performance adjustment, the performance adjustment of Oracle cannot be left blank. Complete categories and functions. The adjustment of the share pool is refined to the adjustment of dictionary cache, library cache, and big pool; the adjustment of physical I/O is more refined to physical datafile, dbw0, redo log, lgwr, ckpt, archive, sort, rollback segment, etc. The database management system, SQL Server 2000, Sybase, and even DB2 are not so detailed! Adjusting SQL statements and application design is the most difficult part of this course. If you have a good understanding of the compilation principles before, it will be helpful. Oracle has also made special optimizations for multi-CPU systems, such as latch, process, MTS, and LRU parameter settings. In this course, some of the uncommon options in the statements learned in database management are described in detail. For example, the nosort option in Table creation and index is used to reduce the use of sorting. Another example is the cache option. When creating and alter table, the cache is added to put the table in the most-recently-used end of LRU lists to improve performance. As mentioned in database management, the specific usage of the analyze command is also deepened, pointing out that it is related to dba_table, dba_index, index_stats, and other tables. We recommend that you use raid in the operating system to improve disk usage efficiency. You can store different files on different disks to reduce the read/write wait time on the disk. There are some operating system usage methods that provide similar measures in Oracle, such as stripe disk, to improve efficiency. The use of indexes mentioned in this article is quite scientific, such as the establishment of reverse indexes and index-organization tables! If you have a clear understanding of many basic concepts in database management, you will be more interested in this course. For example, the concept of snapshot too old cannot be ambiguous! Oracle considers many parameters in init. ora to be very important and you need to understand them, for example, using and setting large_pool_size. This is also important for developers, enabling Program Members pay more attention to programming from the perspective of improving the efficiency of database operation. From my personal point of view, this course is the most worth reading. It is a summary and sublimation of all concepts.

 

In my opinion, as long as it takes three months to read a book carefully, it should be okay to pass the ocp dba examination. In addition, it is necessary to read English documents directly to save time. None of the documents on the DBA examination were translated, and some were missing!

From the practical point of view, the knowledge that can be used in the work may be about 30% of the total capacity of the examination. However, Oracle's methods to implement these functions represent the ideas and models applied by many IT vendors. Understanding the principles of Oracle is conducive to understanding the use of other IT products.