Table Point in Time Recovery using RMAN

Prior to 12c, in case a table or partition is dropped accidentally, there are certain ways to perform the table/partition recovery which includes Flashback database, database point in time recovery and tablespace point in time recovery. 

Starting 12c we can perform point-in-time recovery for a single table

Oracle Snapshot Standby Database

Starting 11g, we can convert a physical standby database into a snapshot standby database. It actually means that we can open a standby database in read-write mode for transactions processing and then later we can convert this database back to standby database. This is accomplished by enabling the database flashback on standby database;

Basic Linux Commands for DBAs

DBAs need some basic commands on Linux to better administer the database and server. Here I will be discussing a few of these commands. 

Checking Uptime
`uptime` command shows; since when server is up and running. It also shows current load average (1 minute, 5 minute and 15 minute)

Installing Oracle Linux 7 for DBAs

Being a DBA, it is good to be independent of system admin as much as you can because many times you could be in a situation where you need to install and/or manage the OS yourself and also need to suggest some OS tuning or parameter setting to run Oracle successfully on your system. Here I will be explaining how to install Oracle Linux 7 on a server.

ORA-01555 Snapshot Too Old

ORA-01555 is one of the most common error messages faced by the DBAs when they receive complains of failing SQLs with this error message. Alert log may contain a message as follows

############################
ORA-01555 caused by SQL statement below (SQL ID: 1f345hftyx6hq,

ORA-00054 resource busy and acquire with NOWAIT specified or timeout expired

While altering or dropping CONSTRAINTS, COLUMNS or INDEXES, you may face error ORA-00054 message and the reason of this error message is current ongoing transaction(s) on the table.

Following are the examples

SQL>  alter table test_tab set unused (name);