ORACLE DBA

                                                Oracle 10g: New Flashback Features by Srinivas Bolisetty Introduction Although the Flashback feature was introduced in Oracle9i, it was limited to Flashback Query only. Great improvements have been made in the Flashback functions in Oracle Database 10g. When user errors and logical corruptions occur in the 10g database, Flashback functionalities provide fast and flexible data recovery. Here is a list of new Flashback features in Oracle Database 10g: • Flashback Database • Flashback Drop • Flashback Table • Flashback Version Query • Flashback Transaction Query In the first part of this series, we are going to introduce two Flashback features, Flashback Database and Flashback Drop. Flashback Database Flashback Database is faster than traditional point-in-time recovery. The traditional recovery method use...

The Oracle Clusterware includes two important components: the voting disk and the Oracle Cluster Registry (OCR). The voting disk is a file that manages information about node membership and the OCR is a file that manages cluster and RAC database configuration information. Oracle recommends that you select the option to configure multiple voting disks during Oracle Clusterware installation to improve availability. Backing up Voting Disks Run the following command to back up a voting disk. Perform this operation on every voting disk as needed where voting_disk_name is the name of the active voting disk and backup_file_name is the name of the file to which you want to back up the voting disk contents: dd if=voting_disk_name of=backup_file_name Recovering Voting Disks Run the following command to recover a voting disk where backup_file_name is the name of the voting disk backup file and voting_disk_name is the name of the active voting disk: dd if=backup_file_name of=voting...

AWR Reports Introduction Workload Repository Reports AWR Snapshots and Baselines Moving AWR Information Reading the AWR Report Useful Queries Remove and Disable AWR Links with AWR Analyzer Introduction AWR periodically gathers and stores system activity and workload data which is then analyzed by ADDM. Every layer of Oracle is equipped with instrumentation that gathers information on workload which will then be used to make self-managing decisions. AWR is the place where this data is stored. AWR looks periodically at the system performance (by default every 60 minutes) and stores the information found (by default up to 7 days). AWR runs by default and Oracle states that it does not add a noticeable level of overhead. A new background server process (MMON) takes snapshots of the in-memory database statistics (much like STATSPACK) and stores this information in the repository. MMON also provides Oracle10G with a server initiated alert feature, which notifies database admini...

Oracle Database 10g Real Application Clusters Handbook ..                                                                         By K. Gopalakrishnan http://books.google.co.in/books?id=2jRSgNZgKnMC&pg=PA129&lpg=PA129&dq=10g+rac+administration+by+gopalakrishna&source=bl&ots=g4G9e5HMnr&sig=BxYDLJkUL561QQvYUtxNVjm2BOY&hl=en&ei=MyrETKvqHYqEvgPewLjbCA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBkQ6AEwAA#v=onepage&q&f=false

Backup and Recovery of OCR (Oracle Cluster Registry) in RAC Tips and technical articles of Oracle RAC DBA OCR calls Oracle Cluster Registry. It stores cluster configuration information. It is also shared disk component. It must be accessed by all nodes in cluster environment.It also keeps information of Which database instance run on which nodes and which service runs on which database.The process daemon OCSSd manages the configuration info in OCR and maintains the changes to cluster in the registry. Automatic Backup of OCR Automatic backup of OCR is done by CRSD process and every 3 hours. Default location is CRS_home/cdata/cluster_name. But we can change default location of this backup of OCR. We can check default location using following command. $ocrconfig -showbackup We can change this default location of physical OCR copies using following command. $ocrconfig -backuploc ...

Virtual IP vip in Oracle RAC : Tips and technical articles of Oracle RAC DBA Oracle Real Application Cluster (Oracle RAC) Virtual IP (vip). How new connection establish in Oracle RAC? For failover configuration we should need to configure our physical ip of host name in listener configuration. Listener process is accepting new connection request and handover user process to server process or dispatcher process in Oracle. Means using listener new connection is being established by Oracle. Once connection get established there is no need of listener process. If new connection is trying to get session in database and listener is down then what will be happening. User process gets error message and connection fails. Because listener is down in same host or something else problem. But in Oracle RAC database environment database is in sharing mode. Oracle RAC database is shared by all connected nodes. Means more th...

Oracle RAC Basic Architecture Part-1: What is Cluster? Cluster consists of two or more independent nodes. Cluster software hides structure of nodes. Due to cluster software all nodes are acting as single server. What is Real Application Cluster? It is component of Oracle for managing two or more instances on different node which are sharing single database. RAC software manages data access and makes consistent image of database. What is Node? Each node contains separate CPU and memory and self contained server in cluster. It contains single instance of RAC database. What is Interconnect? Using cluster interconnect each node communicates messages to other nodes. In short using interconnect all nodes are talking to each other. Interconnect transfers all messages of database from all connected nodes. What is Shar...

Tips and technical articles of Oracle DBA This article is specially for remote dba who are working on 24*7 running large databases. Full table scan is always degrading performance of Oracle database. For troubleshooting of this issues are very important for remote dba. Because When we are using "like" operator in where condition in query. Oracle skips index scanning and performs full table scan. If you are using hint of index in query will also bypass index object. Full table scanning may be decrease performance of query when large table involved. Normal btree index doesn't accessed by Oracle when "like" operator used in where condition with "%" search string. Oracle ConText Cartridge introduced in Oracle8.1.5 and it was called as interMedia Text. CTXSYS schema provides strong search, retrieve and accessing capabilities for text stored in Oracle database. ConText also provides advance linguistic processing ...