(Continued from previous part...)
WHAT EXACTLY IS A DBA? (2)
KNOWLEDGE REQUIRED OF A DBA
A good DBA candidate will know all of the areas discussed above. To reiterate the areas of knowledge required for a DBA are:
* Installation
* Configuration management
* Security
* Monitoring and Tuning
* Backup and Recovery
* Trouble Shooting
A DBA must be familiar with both installation and update on the platform that your system is running against. Each platform has its own quirks and idiosyncrasies. A DBA experienced on Windows-NT will have difficulty performing an installation on UNIX or DEC-VMS. Updates can raise havoc with production machines if they are done incorrectly. DBA candidates should be able to answer specific questions concerning installation and upgrade of Oracle systems on your platform. They should exhibit the curiosity to ask about your platform and any modifications to the standard installation that exist upon it during the interview process.
Configuration management involves database sizing, file placement and specification of storage media. A full--charge DBA will be familiar with system topics such as RAID levels, disk sharing, disk shadowing, solid state disks, optical storage and their application to the Oracle database environment. On UNIX they should also be familiar with the cost and benefits associated with use of raw devices and when raw device usage is mandatory.
Understanding Oracle security options is vital to the DBA job. A demonstrated knowledge of system and object level privileges, roles and profiles is required for any DBA. Understanding how the operating system security options interface with the Oracle options is also important. Additional requirements such as use of Secure Oracle and implementation of SQLNET are also considerations.
One of the critical aspects of the DBA job is the monitoring and tuning of the database and any applications. Monitoring and tuning requires a detailed understanding of the Oracle data dictionary, the tkprof and explain plan utilities and understanding how both the cost based and rule based optimizers function. Detailed understanding of what can an can't be done via indexing, use of hints and SQL statement tuning is vital to a DBA. A DBA candidate should demonstrate knowledge of:
* DBA_ views, ALL_ views and USER_ views
* SYS owned "$" tables
* V$ dynamic performance tables
all of these are a part of the Oracle data dictionary. In addition the DBA candidate should have knowledge of the DBMS_* series of packages and how they can be used to facilitate tuning and script development and the UTL*.SQL series of utility scripts and their usage in tuning and monitoring.
A DBA candidate must understand all of the backup and recovery options. Use of the import and export utilities, use of cold and hot backups, all of these are vital topics that a DBA must understand. Interview questions concerning types of database backups used and how the utilities can be used are in order to show level of knowledge in this area. An additional
topic that should be covered in this phase of the interview are recovery scenarios involving partial recovery at the table, tablespace and database levels.
Troubleshooting is a binary ability. Usually people will either have the knack or they won't. Troubleshooting requires an analytical approach where the problem is laid out in discrete parts and each is attacked in a methodological fashion until the problem is solved. Troubleshooting also involves the ability to admit when you don't know something but having the tenacity to say "But I can look it up". Questions on troubleshooting must come from real life and should involve multiple steps and thought to solve. Questions on the most difficult problem they have encountered and how they solved it are in order to test their troubleshooting ability.
A final bit of knowledge required of a DBA is the ability to communicate clearly either in word or via written materials. Since a major portion of a DBA job will involve interaction with others on multiple levels within a company environment your DBA must speak, think and write clearly and concisely. A review of their resume with particular attention to any publishing credits will help with determining their abilities in this regard. Presentations at user groups, local or national, magazine articles or just articles in local user group publications all show the ability to communicate. At a professional level look for jobs where they wrote documentation or procedures. Most candidates with advanced degrees such as Masters or Phds will have had to have written and communicate to get to that level of education. Ask them to bring their dissertation or examples of their writing to the interview. Candidates should be sure to bring examples of this type of ability to the interview. The ability to communicate clearly in spoken word is also vital, the ability to take and give instructions and to understand complaints is vital. As qualified technically as a candidate may be if they cannot communicate they will not succeed.
Sources of DBA Certification Information
Oracle
http://www.oracle.com/education/certification/
Microsoft SQL Server
http://www.microsoft.com/trainingandservices/default.asp?PageID=training
IBM DB2
http://www.ibm.com/certify
Sybase Adaptive Server
http://www.sybase.com/education/profcert/
Informix
http://www-3.ibm.com/software/data/informix/education
(Continued on next part...)
