How to find DB links in Oracle??

select * from DBA_DB_LINKS   - All DB links defined in the database.
select * from ALL_DB_LINKS    - All DB links the current user has access to.
select * from USER_DB_LINKS - All DB links owned by current user.

Create user

CREATE USER TEST_SUH IDENTIFIED BY whoami
DEFAULT TABLESPACE users_tbs
TEMPORARY TABLESPACE temp
QUOTA 100M ON users_tbs
QUOTA UNLIMITED ON data_tbs;

Create tablespace: Temporary Tablespace

CREATE TABLESPACE temp_tbs TEMPFILE '/opt/oracle/mydbs/data/mydbs_temp_tbs_01.tmp' SIZE 100m;

Create tablespace: Undo Tablespace

CREATE TABLESPACE undo_tbs TEMPFILE '/opt/oracle/mydbs/data/mydbs_undo_tbs_01.tmp' SIZE 1g RETENTION GUARANTEE;

Create tablespace: Permanent Tablespace

CREATE TABLESPACE data_tbs DATAFILE '/opt/oracle/mydbs/data/mydbs_data_tbs_01.dbf' SIZE 100m;
CREATE TABLESPACE data_tbs DATAFILE '/opt/oracle/mydbs/data/mydbs_data_tbs_01.dbf' SIZE 100m FORCE LOGGING BLOCKSIZE 8k;
CREATE TABLESPACE data_tbs DATAFILE '/opt/oracle/mydbs/data/mydbs_data_tbs_01.dbf' SIZE 100m NOLOGGING DEFAULT COMPRESS EXTENT MANAGEMENT LOCAL UNIFORM SIZE 1M;
CREATE TABLESPACE data_tbs DATAFILE '/opt/oracle/mydbs/data/mydbs_data_tbs_01.dbf' SIZE 100m NOLOGGING
DEFAULT COMPRESS EXTENT MANAGEMENT LOCAL AUTOALLOCATE SEGMENT SPACE MANAGEMENT AUTO;
CREATE BIGFILE TABLESPACE data_tbs DATAFILE '/opt/oracle/mydbs/data/mydbs_data_tbs_01.dbf' SIZE 10G;

Create spfile

CREATE SPFILE FROM PFILE;
CREATE SPFILE='/opt/oracle/admin/mydb/pfile/spfilemybd.ora' FROM PFILE='/opt/oracle/admin/mydb/pfile/initmybd.ora';

Create profile

CREATE PROFILE development_profile
LIMIT
SESSIONS_PER_USER 2 CONNECT_TIME 100000 IDLE_TIME 100000
LOGICAL_READS_PER_SESSION 1000000
PRIVATE_SGA 10m
FAILED_LOGIN_ATTEMPTS 3
PASSWORD_LIFE_TIME 60
PASSWORD_REUSE_TIME 365
PASSWORD_REUSE_MAX 3
PASSWORD_LOCK_TIME 30
PASSWORD_GRACE_TIME 5;

Create pfile

CREATE PFILE FROM SPFILE;
CREATE PFILE='/opt/oracle/admin/mydb/pfile/initmybd.ora' FROM SPFILE='/opt/oracle/admin/mydb/pfile/spfilemybd.ora';

Create/Delete database link

CREATE:
CREATE DATABASE LINK my_db_link CONNECT TO current_user USING 'my_db';
CREATE PUBLIC DATABASE LINK my_db_link CONNECT TO remote_user IDENTIFIED BY psicorp
USING 'my_db';
DROP:
DROP DATABASE LINK my_db_link;

DROP PUBLIC DATABASE LINK my_db_link;

Create directory

CREATE OR REPLACE DIRECTORY mydir AS '/opt/oracle/admin/directories/mydir';

Create database

CREATE DATABASE prodb
MAXINSTANCES 1 MAXLOGHISTORY 1
MAXLOGFILES 5 MAXLOGMEMBERS 3
MAXDATAFILES 100
DATAFILE 'C:\oracle\ora92010\prodb\system01.dbf'
SIZE 250M REUSE AUTOEXTEND ON NEXT 10240K
MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL DEFAULT
TEMPORARY TABLESPACE TEMP
TEMPFILE 'C:\oracle\ora92010\prodb\temp01.dbf'
SIZE 40M REUSE AUTOEXTEND ON NEXT 640K MAXSIZE UNLIMITED
SYSAUX TABLESPACE
DATAFILE 'C:\oracle\ora92010\prodb\sysauxtbs01.dbf'
SIZE 300M REUSE AUTOEXTEND ON NEXT 5120K MAXSIZE UNLIMITED
UNDO TABLESPACE "UNDOTBS1"
DATAFILE 'C:\oracle\ora92010\prodb\undotbs01.dbf'
SIZE 200M REUSE AUTOEXTEND ON NEXT 5120K MAXSIZE UNLIMITED
CHARACTER SET WE8MSWIN1252
NATIONAL CHARACTER SET AL16UTF16
LOGFILE
GROUP 1 ('C:\oracle\ora92010\prodb\redo01.log') SIZE 102400K,
GROUP 2 ('C:\oracle\ora92010\prodb\redo02.log') SIZE 102400K,
GROUP 3 ('C:\oracle\ora92010\prodb\redo03.log') SIZE 102400K;

Create control file

CREATE CONTROLFILE REUSE DATABASE "mydb" 
NORESETLOGS NOARCHIVELOG
MAXLOGFILES 32 MAXLOGMEMBERS 3
MAXDATAFILES 200 MAXINSTANCES 1
MAXLOGHISTORY 1000
LOGFILE
GROUP 1 ('/ora01/oracle/mydb/mydb_redo1a.rdo',
              '/ora02/oracle/mydb/mydb_redo1b.rdo') SIZE 500K,
GROUP 2 ('/ora01/oracle/mydb/mydb_redo2a.rdo',
              '/ora01/oracle/mydb/mydb_redo2b.rdo') SIZE 500K
DATAFILE
'/ora01/oracle/mydb/mydb_system_01.dbf ',
'/ora01/oracle/mydb/mydb_users_01.dbf ',
'/ora01/oracle/mydb/mydb_undo_01.dbf ',
'/ora01/oracle/mydb/mydb_sysaux_01.dbf ',
'/ora01/oracle/mydb/mydb_alldata_01.dbf ';

Alter user: Password and Account Management

ALTER USER olduser PASSWORD EXPIRE;
ALTER USER olduser ACCOUNT LOCK;
ALTER USER olduser ACCOUNT UNLOCK;

Alter trigger

ALTER TRIGGER tr_my_trigger DISABLE;
ALTER TRIGGER tr_my_trigger ENABLE;
ALTER TRIGGER tr_my_trigger RENAME TO tr_new_my_trigger;
ALTER TRIGGER tr_my_trigger COMPILE;

Alter user: Change Password

ALTER USER olduser IDENTIFIED BY newpassword;
ALTER USER olduser IDENTIFIED EXTERNALLY;

Alter tablespace: Tablespace Management

ALTER TABLESPACE my_data_tbs DEFAULT STORAGE (INITIAL 100m NEXT 100m FREELISTS 3);
ALTER TABLESPACE my_data_tbs MINIMUM EXTENT 500k;
ALTER TABLESPACE my_data_tbs RESIZE 100m;
ALTER TABLESPACE my_data_tbs COALESCE;
ALTER TABLESPACE my_data_tbs OFFLINE;
ALTER TABLESPACE my_data_tbs ONLINE;
ALTER TABLESPACE mytbs READ ONLY;
ALTER TABLESPACE mytbs READ WRITE;
ALTER TABLESPACE mytbs FORCE LOGGING;
ALTER TABLESPACE mytbs NOLOGGING;
ALTER TABLESPACE mytbs FLASHBACK ON;
ALTER TABLESPACE mytbs FLASHBACK OFF;
ALTER TABLESPACE mytbs RETENTION GUARANTEE;
ALTER TABLESPACE mytbs RETENTION NOGUARANTEE;

Alter tablespace: Rename

ALTER TABLESPACE my_data_tbs RENAME TO my_newdata_tbs;

Alter tablespace: Data Files and Tempfiles

ALTER TABLESPACE mytbs ADD DATAFILE /ora100/oracle/mydb/mydb_mytbs_01.dbf' SIZE 100M;
ALTER TABLESPACE mytemp ADD TEMPFILE '/ora100/oracle/mydb/mydb_mytemp_01.dbf' SIZE 100M;
ALTER TABLESPACE mytemp AUTOEXTEND OFF;
ALTER TABLESPACE mytemp AUTOEXTEND ON NEXT 100m MAXSIZE 1G;

Alter tablespace: Backups

ALTER TABLESPACE my_data_tbs BEGIN BACKUP;
ALTER TABLESPACE my_data_tbs END BACKUP;

Alter system: System Management

ALTER SYSTEM CHECKPOINT GLOBAL;
ALTER SYSTEM KILL SESSION '145,334';
ALTER SYSTEM ENABLE RESTRICTED SESSION;
ALTER SYSTEM DISABLE RESTRICTED SESSION;
ALTER SYSTEM SUSPEND;
ALTER SYSTEM QUIESCE RESTRICTED;
ALTER SYSTEM UNQUIESCE;
ALTER SYSTEM RESUME;
ALTER SYSTEM FLUSH SHARED_POOL;
ALTER SYSTEM FLUSH BUFFER_CACHE;