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• quick guide to Oracle backup and recovery • using explain plan • primary keys versus unique indexes in Oracle From: Hatem AHRIZ - Is the EXPLAIN PLAN command only available to DBAs? PS. The utlxplan.sql script is only available on the server. Explain plan is available to all users of teh Oracle database as long as the DBA has created and granted access to the plan table (and created a public synonym for it). Type "Desc plan_table" in sql*plus. If it doesn't exist ask the DBA to create it and/or grant access to it and/or create a synonym for it. The utlxplan.sql script is used to create the plan table in the user's schema. --------- From: RvNair Hello, i know that primary key means not null & unique key means i can store null value,but then why is primary key considered better than unique key?plz help me thanx in advance, The other major difference between primary keys and unique keys in Oracle is that a table can have only 1 primary key, although this may be a composite key (composed of more than one column), but can have any number of unique keys. The primary key constraint is supported automatically by a unique index and represents the primary access route for the table, secondary indexes can be unique or non-unique. For example the table "department" might have a primary key of "id" and might have a secondary unique index on "name". These indexes would ensure that the department id is unique and not null and that the department name is unique. --------- From: Narayan - please help me with backup & recovery in oracle9i  The easiest way to take a backup of an Oracle database irrespective of which version you're using is to do a full cold backup, also known as an offline backup. This involves shutting down the database cleanly - by entering one of the commands shutdown normal, shutdown immediate or shutdown transanctional, or using Oracle Enterprise Manager -  and then using operating system commands to copy the data files, control files, redo log files and the parameter file to another disk or to tape. In the event of an incident requiring recovery of the database, you will be able to restore it to the point at which the last backup was taken by copying the files back to their original location. Other backup methods include on-line backups, made whilst the database is still open, by puting a tablepsace into backup mode temporarily (to suspend writes to objects in that tablespace) so that the files belonging to the tablespace can be copied. This also requires the database to be running in archivelog mode, so that the redo logs are archived as they are filled before they are overwritten. Recovery in this case, involves restoring the lost/corrupted data files and then recovering the database using the archived log files. The Recovery Manager utility (RMAN) can be used to make database backup (and recovery) easier. Both of these methods are physical backups. Logical backups can be made using the export utility (or DataPump utility available in Oracle 10g and above) and database objects (tables,indexes,constraints etc) recovered using import. The export utility can be used to backup the whole database, the objects belonging to one or more specified users, or a specified set of tables (and associated indexes). In Oracle 9i and above, export can be used to backup all the objects in a specified tablespace. For recommendations on books explaining backup and recovery and other subjects, see our Oracle resources page. For training in backup and recovery see our scheduled Oracle training courses. --------- Use the contact form to send us your questions and feedback or to subscribe just click here. For more Oracle help, see the many free articles and tutorials we have on our site. We also offer Oracle training for developers and dbas both on and off site. The resources page has recommendations for further reading to enhance your knowledge of Oracle and contains links to information on OTN and other places.  --------------------------------------- Looking to sky-rocket productivity, save time and reduce costs?Training is a highly cost-effective and proven method of boosting productivity.  Smartsoft offers instructor-led training in Oracle and related technologies on or off site in cities across the UK as well as self-study online training.  See our scheduled Oracle training courses, or let us know your requirements. Oracle tips and tricks Subscribe to our newsletter, jam-packed full of tips and tricks to help you slash costs, sky-rocket productivity and make your systems better, faster and smarter. © Smartsoft Computing Ltd, Bristol, England Need help? Contact Us This site uses woopra.com to gather statistical information about our visitors. This data is aggregated to show industry trends (such as browser share). 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