This blog post is part of the “RMAN Back to Basics” series, which can be found here.
Introduction
In order for an Oracle Database to be resilient to physical storage failures, i.e. disk failure, it is imperative that the database files are placed according to Best Practice, so to avoid loss of database in case of a storage failure. For example, don’t have your database and backups on the same disk, because if the disk fails, you have no means to resolve the failure.
This blog post will advise which files need to be protected and how, followed by a demo of creating a new database which shows how Oracle conforms to the best practice when setting a few parameters.
What files comprise a database?
An Oracle database comprises of the following files:
- spfile
- password file
- control files*
- datafiles including temp files
- redo logs*
The files marked with * should be multiplexed over a minimum of 2 locations:
Automatic Storage Management (ASM): +DATA and +FRA
- If HIGH redundancy, Oracle say to use 1 control file and log member to reduce the control file and log file writes. However this is Availability vs Performance, if Data Guard is in place then this is a more viable recommendation to have 1, but I recommend still to multiple.
Oracle Managed Files: /oradata and /fast_recovery_area
- Can be prefixed with the Oracle default of /u01/app/oracle as long as the oradata and fast_recovery_area are physically different, i.e. mounts to different disks or mounts to SAN/NAS.
Once the above is conformed to, you will be able to resolve any issues from any scenario, assuming you take backups 🙂
Create Database Demo
Below we create a database called ZEDDBA, using my createZEDDBA.sh script:
[oracle@dc1sbxdb001 scripts]$ ./createZEDDBA.sh ------------------------------ Step 1: Add Database to oratab ------------------------------ Press Enter to continue adding ZEDDBA to oratab... Databases in oratab: ZEDDBA:/u01/app/oracle/product/12.2.0/dbhome_1:N Setting the Database Environment using oraenv... The Oracle base has been set to /u01/app/oracle ORACLE_SID: ZEDDBA ORACLE_HOME: /u01/app/oracle/product/12.2.0/dbhome_1 Press Enter to continue
The script adds the line:
ZEDDBA:/u01/app/oracle/product/12.2.0/dbhome_1:N
To the oratab and then sets the environment by using .oraenv in slient mode.
Next the pfile is created from the content shown below:
-------------------- Step 2: Create pfile -------------------- Press Enter to continue Content of pfile just created: db_name='ZEDDBA' memory_target=2816M processes = 150 db_block_size=8192 db_create_file_dest='/u01/app/oracle/oradata' db_domain='' db_recovery_file_dest='/u01/app/oracle/fast_recovery_area' db_recovery_file_dest_size=10G diagnostic_dest='u01/app/oracle' dispatchers='(PROTOCOL=TCP) (SERVICE=ZEDDBAXDB)' open_cursors=300 remote_login_passwordfile='EXCLUSIVE' undo_tablespace='UNDOTBS1' compatible ='12.2.0.1' Press Enter to continue -------------------------------- Step 3: Create spfile from pfile -------------------------------- Press Enter to continue Calling 'sqlplus / as sysdba' And running 'create spfile from pfile;' File created. Press Enter to continue
PLEASE NOTE: The lines highlighted in red, are the minimum parameters required for Oracle to use Oracle Managed Files (OMF) and multiplex critical files. This example shows both paths under ‘/u01‘ as an example, which is fine as long as the ‘oradata‘ and ‘fast_recovery_area‘ are physically different as explained earlier on. They could also be under ‘/u02/oradata‘ for oradata and ‘/u03/fast_recovery_area‘ for fast_recovery_area, which is my personal preference, leaving ‘/u01‘ for oracle binaries.
Next the instance is started in nomount, so to spawn the processes and create the memory structure but not attempt to access controlfiles or datafiles as they do not exist as yet:
------------------------------------- Step 4: Start the instance in nomount ------------------------------------- Press Enter to continue Calling 'sqlplus / as sysdba' And running 'startup nomount;' ORACLE instance started. Total System Global Area 2952790016 bytes Fixed Size 8625080 bytes Variable Size 1677722696 bytes Database Buffers 1258291200 bytes Redo Buffers 8151040 bytes Press Enter to continue
Next the database is created using the create database statement:
------------------------------------------------------- Step 5: Create database using create database statement ------------------------------------------------------- Press Enter to continue Content of createZEDDBA.sql just created: CREATE DATABASE ZEDDBA USER SYS IDENTIFIED BY oracle USER SYSTEM IDENTIFIED BY oracle CHARACTER SET AL32UTF8 NATIONAL CHARACTER SET AL16UTF16 EXTENT MANAGEMENT LOCAL DEFAULT TABLESPACE users DEFAULT TEMPORARY TABLESPACE tempts1 UNDO TABLESPACE undotbs1; Press Enter to continue Calling 'sqlplus / as sysdba' And running '@?/dbs/createZEDDBA.sql' Database created. Press Enter to continue
Please Note: I haven’t specified any control files, datafiles or redo logs. Oracle will automatically create them based on the settings mentioned earlier.
Next we show the database layout:
---------------------------- Step 6: Show database layout ---------------------------- Press Enter to continue Calling 'sqlplus / as sysdba' And running '@?/dbs/showfiles.sql' Showing 'select name from v$controlfile;' Press Enter to continue NAME ---------------------------------------------------------------------------------------------------- /u01/app/oracle/oradata/ZEDDBA/controlfile/o1_mf_gftkqxjg_.ctl /u01/app/oracle/fast_recovery_area/ZEDDBA/controlfile/o1_mf_gftkqxof_.ctl Showing 'select GROUP#, TYPE, MEMBER, IS_RECOVERY_DEST_FILE from v$logfile;' Press Enter to continue GROUP# TYPE MEMBER IS_ ---------- ------- -------------------------------------------------------------------------------- --- 1 ONLINE /u01/app/oracle/oradata/ZEDDBA/onlinelog/o1_mf_1_gftkqy26_.log NO 1 ONLINE /u01/app/oracle/fast_recovery_area/ZEDDBA/onlinelog/o1_mf_1_gftkqzk3_.log YES 2 ONLINE /u01/app/oracle/oradata/ZEDDBA/onlinelog/o1_mf_2_gftkqztn_.log NO 2 ONLINE /u01/app/oracle/fast_recovery_area/ZEDDBA/onlinelog/o1_mf_2_gftkr1x7_.log YES Showing 'select name from v$datafile;' Press Enter to continue NAME ---------------------------------------------------------------------------------------------------- /u01/app/oracle/oradata/ZEDDBA/datafile/o1_mf_system_gftkr3fv_.dbf /u01/app/oracle/oradata/ZEDDBA/datafile/o1_mf_sysaux_gftkr792_.dbf /u01/app/oracle/oradata/ZEDDBA/datafile/o1_mf_undotbs1_gftkr944_.dbf /u01/app/oracle/oradata/ZEDDBA/datafile/o1_mf_users_gftkr9fc_.dbf Showing 'select name from v$tempfile;' Press Enter to continue NAME ---------------------------------------------------------------------------------------------------- /u01/app/oracle/oradata/ZEDDBA/datafile/o1_mf_tempts1_gftkr9c7_.tmp Press Enter to exit sqlplus Press Enter to continue
As you can see the control files and redo logs have automatically multiplexed over ‘oradata‘ and ‘fast_recovery_area‘, where as the rest are in ‘oradata‘. When backups are taken, they will be in ‘fast_recovery_area‘ which allows for control file and datafiles to be recovered in case of lost of ‘oradata‘ once the physical issue is resolved.
Finally run the rest of the script to run the catelog.sql, cateproc.sql, datapatch, etc to complete the database creation:
---------------------------------------------------- Step 7: run catalog.sql, catproc.sql, datapatch, etc ---------------------------------------------------- Press Enter to continue ... ... ... Session altered. SQL Patching tool version 12.2.0.1.0 Production on Thu May 16 12:50:03 2019 Copyright (c) 2012, 2017, Oracle. All rights reserved. Log file for this invocation: /u01/app/oracle/cfgtoollogs/sqlpatch/sqlpatch_10329_2019_05_16_12_50_03/sqlpatch_invocation.log Connecting to database...OK Bootstrapping registry and package to current versions...done Determining current state...done Current state of SQL patches: Patch 25811364 (OJVM RELEASE UPDATE: 12.2.0.1.170718 (25811364)): Installed in the binary registry only Bundle series DBRU: ID 170814 in the binary registry and not installed in the SQL registry Adding patches to installation queue and performing prereq checks... Installation queue: Nothing to roll back The following patches will be applied: 25811364 (OJVM RELEASE UPDATE: 12.2.0.1.170718 (25811364)) 26609817 (DATABASE RELEASE UPDATE 12.2.0.1.170814) Installing patches... Patch installation complete. Total patches installed: 2 Validating logfiles... Patch 25811364 apply: SUCCESS logfile: /u01/app/oracle/cfgtoollogs/sqlpatch/25811364/21188920/25811364_apply_ZEDDBA_2019May16_12_50_21.log (no errors) Patch 26609817 apply: SUCCESS logfile: /u01/app/oracle/cfgtoollogs/sqlpatch/26609817/21483023/26609817_apply_ZEDDBA_2019May16_12_50_21.log (no errors) SQL Patching tool complete on Thu May 16 12:50:38 2019 Start Time: 16-05-2019_12_20 En Time: 16-05-2019_12_50 Press Enter to exit shell script [oracle@dc1sbxdb001 scripts]$
Reference
Scripts
To download all 5 in one zip: createZEDDBA.zip
The above demo is based on Oracle Database 12cR2, installed under “/u01/app/oracle/product/12.2.0/dbhome_1“. Scripts under “/media/sf_Software/scripts/” which I am running Oracle Linux 7.4 on VirtualBox. Some modification may be required to work in your environment.
The rest of the series
- Oracle Database File Placement Best Practice & Create Database Demo
- RMAN Full Backup & Demo
- RMAN Image Copy & Demo
- RMAN Incremental & Demo Part 1 (Level 0)
- RMAN Incremental & Demo Part 2 (Level 1)
- RMAN Incremental with Block Change Tracking & Demo
- RMAN Incremental Differential vs Cumulative & Demo
- RMAN Incremental Updating Backup & Demo Part 1
- RMAN Incremental Updating Backup & Demo Part 2
- Flashback
- RMAN Block Media Recovery
- RMAN Recover database with only FRA
- RMAN Obsolete
Please Note: Links to the blog posts will be released daily and updated here.
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Thanks
Zed DBA (Zahid Anwar)
Zed DBA's Oracle Blog 