Backup

The flip side of recovery

Types of Failures

• Transaction failure– Transaction must be aborted

• System failure– Hardware or software problem

resulting in volatile memory loss• Media failure

– Disks or tapes• Disasters

Backup Methods

• Physical (block by block copy)– Cold

• db is shutdown, files are not changing• shutdown instance, backup files (datafiles,

control files, parameter files, redo logs & archive logs), start db

– Hot• db is open and files are being used• each tablespace is put into “backup” mode in

turn and then backed up using RMAN or EBU, then put back online

• MUST have archive logging on to use this method

Backup Methods (cont.)

• Logical (actually reads data)– Export

• Rebuild scripts– Use to re-create the structure of the

database– control file create script

• alter database backup controlfile to trace noresetlogs;

– database create script– roles and users create scripts

So what’s best?• Use a combination of options

• If must have point in time recovery, run with archive logging ENABLED

• Additional points– mirror control files and redo logs– keep as many archive logs on disk as possible– disk copies of backup files and archive logs should

be on their own disk– make backups of control files if db structure

changes!

• Can stage backups so they go faster (disk to disk to tape)

• TEST, TEST, TEST!

Developing a backup strategy...

• Points to consider– downtime– backup window– types of failures

• power loss, disk, natural disaster, human error?

– recovery time– retention time

• Basic database setup

You are the DBA...

• 24x7 database (or very small backup window)

• need fast recovery• need ability to recover db objects• need point in time recovery

More db availability options• 3-way mirror of db

– expensive in disk space, but very safe

• Hot standby database– copy of db is created, logs from primary db

are applied directly to the copy

• Replicated database– db is copied through snapshots or through

replication rules– if replicated, transactions can occur against

both copies of the db - must have conflict resolution in place!

And Recovery...• Determine what kind of recovery is required

– instance recovery or process recovery (restart the db)

– user error recovery or statement failure recovery (fixing affected transaction only)

– media recovery• which files are destroyed?• recover database, tablespace or datafile?• resetlogs?

• Before doing recovery, perform precautionary backup

• ALWAYS backup after recovery

Disaster recovery planning

• Situation and response• Include triggers and contacts

• Backup/redundant hardware?• Off site hardware and facilities?• Off site backups?

Security, Roles, and Privileges

• Object vs. system (access) privileges

• roles– privilege “groupings”– can have other roles granted to them

• basic procedure– create user– create role– grant privs to role– grant role to user

Predefined roles– DBA

• create, alter, drop anything (user, procedure, table, etc.)• select, insert, update, delete or lock any table or view• force any transaction• execute any package, trigger, procedure• grant any privelege or role, become any user• backup any tablespace/table• audit anything, analyze anything, restrict or kill sessions

– Connect• alter session• create database link, sequence, session, synonym, table,

view

– Resource• create procedure, sequence, table, trigger

PUBLIC

• Never grant to PUBLIC with grant or admin option

• Not wise to grant anything other than SELECT to PUBLIC

• PUBLIC should not own any data object

• PUBLIC may own synonyms and views

Finding Privileges and Roles

• Dba_users, dba_tab_privs, dba_sys_privs, dba_role_privs

• With admin option

• sec_obj.sql• sec_priv.sql• sec_role.sql

Profiles

• In Oracle 8, can set up profiles to impose resource limits, enforce password policies, lock accounts after failed logins, etc.– sessions_per_user, idle_time, cpu_per_session– failed_login_attempts– password_life_time, password_grace_time,

password_verify_function

• dba_profiles

Installing and configuring the client

• Obtain CD from ATN or SILS library• Install software• Configure tnsnames.ora

– Provides all necessary connection information

– Is created automatically when use configuration wizard (last step of install)

– Can be created manually, if desired

Listener.oraTnsnames.ora

client

server

Tnsnames.ora

... (CONNECT_DATA =

(SID = INLS) )...

INLS = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = pearl.ils.unc.edu)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = INLS.ils.unc.edu) ) )

Excerpt from tnsnames.ora [New style (8i)] :

Excerpt from tnsnames.ora [Old style (8 or earlier)] :