Dynamic View - v$session

Session Info

Checksum ** Download software verify utility

It's a common practice to download oracle software from website to your laptops for any installation, upgrades, patching ... however sometimes when you have a interrupting network connection you are left with a question over the file being download is complete?

Utilize the csum command to check if the download file is complete & not corrupted
Example in AIX

$csum p8202632_10205_AIX64-5L_1of2.zip
$csum -h SHA1  p8202632_10205_AIX64-5L_1of2.zip

Compare the output with metadata which is present on OTN if the output matches you are good to go & rest with peace 

RMAN help

List of backupsets

RMAN> list backupset;

list complete backup

RMAN> list backup;

To list summary of backup

RMAN> list backup summary;

List a particular backup set if you know the backup set number

RMAN> list backupset backupset#;
RMAN> list backupset 12;
RMAN> list backupset tag 'tagname';
RMAN> list backup of datafile #;
RMAN> list incarnations;

Enable Automatic Memory Management

Enable AMM

Disable Automatic Memory Management or Enable Automatic Shared Memory Management

Disable AMM & Enable ASMM

SQL help

List Database sessions & their status

Select * from ( Select username,status from V$session where username is not null)  pivot  ( count(status)   for status in ('ACTIVE','INACTIVE','KILLED')) ;

RMAN Queries

V$RMAN_OUTPUT -- details about recent rman jobs

Users with Default passwords

select * from dba_users_with_defpwd; 

Encryption:

select * from v$encrypted_tablespaces ;

select * from dba_encrypted_columns; 

Character Set:
select * from nls_database_parameters;

Check Features:
select name,last_usage_date from dba_feature_usage_statistics where detected_usages>0  order  by 1;