RAC

Oracle RAC Overview

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Real Application Clusters (RAC) is an clustering solution whereby multiple Oracle instances can communicate with one database located on shared storage.
Datafiles and controlfiles are shared but each instance will have its own redo log files and undo tablespace.
Use crsctl to manage the clusterware
Use srvctl to manage the cluster

• cloning oracle home in RAC - Amit Saraswat
• Loss of a voting disk - oracledbasupport.co.uk

Know nothing about RAC? Go through the RAC Attack labs step-by-step installation for 11g RAC_Attack!
or 12c RACAttack for an excellent (hands on) introduction.

• RAC Attack template

How to Backup and Restore a RAC Database

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RAC components

Virtual IP

A virtual IP address is an IP address setup to "float" between the real IP addresses associated with each instance in the cluster. If the IP address assigned to the virtual IP becomes unavailable, the IP address from the still available instance will be assigned to the virtual IP thus maintaining database availability for the users.

Voting Disk

A Voting Disk is a file on a shared filesystem. It maintains a list of available cluster nodes and can resolve split-brain scenarios.
All instances write to the voting disk to indicate that they are still active.

Cluster Registry

The Cluster Registry (OCR) is used to store cluster wide settings and status information such as node names, IP and VIP addresses, voting disk locations, node applications, database names, instance names, listener names, etc.

Clusterware processes

A RAC cluster consists of the following daemons

• crsd – Cluster Resource Services Daemon
• cssd – Cluster Synchronisation Services Daemon
• evmd – Event Manager Daemon

RAC commands

Location of Oracle Local Registry configuration file (olr.loc)

This file points to the clusters local node repository and depending on the OS, it is in one of these 2 locations

cat /etc/oracle/olr.loc
cat /var/loc/oracle/olr.loc

This file is managed by OHASD and will point to the olrconfig_loc and the crs_home

Location of cluster config files

/etc/oracle/scls_scr/$HOSTNAME

Some cluster control commands to check the status / health of the clusterware

crsctl status resource -t
crsctl status server
crsctl check cluster
crsctl check crs
crsctl query css votedisk
crsctl query crs activeversion
crsctl query crs releaseversion
crsctl query crs softwareversion

List network interfaces available to this cluster node

oifcfg iflist -p

Is Oracle Restart (High Availability Service) enabled?

cat /etc/oracle/scls_scr/$HOSTNAME/oracle/ohasdstr
crsctl check has
crsctl config has
crsctl start has
crsctl stop has
crsctl disable has
crsctl enable has

Is ASM autostart enabled?

crsctl stat res ora.asm

Are diskgroups registered?

srvctl status diskgroup -g DATA
crsctl stat res ora.DATA.dg

Is database registered and autostart enabled?

srvctl config database -d <database>

if not...

srvctl add database <database>
srvctl enable database <database>

Set ASM diskgroups to be used by database

srvctl modify database -d <database> -diskgroup "DATA,FRA"

Stop and start the clusterware services

To set the correct home, can also search /etc/oratab for the relevant ASM instance and use . oraenv

export ORA_CRS_HOME=$(awk -F: '/+ASM/ {print $2}' /etc/oratab)
$ORA_CRS_HOME/bin/crsctl start crs
$ORA_CRS_HOME/bin/crsctl stop crs

Prevent cluster services from starting up on boot

$ORA_CRS_HOME/bin/crsctl disable crs

Re-enable clusterware services

$ORA_CRS_HOME/bin/crsctl enable crs

List the resources under cluster control

$ORA_CRS_HOME/bin/crsctl status resource -t
or
$ORA_CRS_HOME/bin/crsctl stat res -t

or

crsctl status res |grep -v "^$"|awk -F "=" 'BEGIN {print " "} {printf("%s",NR%4 ? $2"|" : $2"\n")}'|sed -e 's/  *, /,/g' -e 's/, /,/g'|\
awk -F "|" 'BEGIN { printf "%-40s%-35s%-20s%-50s\n","Resource Name","Resource Type","Target ","State" }{ split ($3,trg,",") split ($4,st,",")}{for (i in trg) {printf "%-40s%-35s%-20s%-50s\n",$1,$2,trg[i],st[i]}}'

Find the ORACLE_HOME from a database cluster metadata file

crsctl stat res ora.proddb11.db -p | grep ORACLE_HOME

Stop all the cluster resources for a particular ORACLE_HOME

If all resources for a home need to go down (e.g. for patching), this should do it.
Save the state so that the start command knows what to start and what not to.

srvctl stop home -o /oracle/product/11.2.0.4 -s /oracle/state_file_11204
or
srvctl stop home -oraclehome /oracle/product/11.2.0.4 -statefile /oracle/state_file_11204
or
srvctl stop home -oraclehome /u01/app/oracle/product/12.1.0.2/dbhome_1 -statefile /home/oracle/home_state_20170111 -node sdtcsynoda02-rac -stopoption IMMEDIATE -force

Before running the startup, the state file can be edited and instances added/removed as it is a simple text file

srvctl start home -o /u01/app/oracle/product/12.1.0.2/dbhome_1 -s /oracle/state_file_12102 -node sdtcsynoda02-rac

General syntax for starting and stopping a RAC instance

srvctl start|stop instance -d <db_unique_name> -i <inst_name_list> [-o start_options]|[-o stop_options]  [-c connect_str | -q]

Stop one instance of a RAC database

srvctl stop instance –d <db_name> –i <instance_name>

Start an ASM instance on a specific node

srvctl start instance –n <node_name>
e.g.
srvctl start prodctl –n asmnode1

Stop all instances of a RAC database

srvctl stop database –db <db_name>
e.g.
srvctl stop database -db ACCINGPX

Start all instances of a RAC database

srvctl start database –db <db_name>
e.g.
srvctl start database -db ACCINGPX

Start a database in mount mode

srvctl start database –db <db_name> -o <start option>
e.g.
srvctl start database -db ACCINGPX -o mount

Stop ASM on a RAC node

srvctl stop asm –n <rac node>
e.g.
srvctl stop asm –n asmnode1 -o immediate

Start / Stop all node applications on a RAC node

srvctl start nodeapps –n <rac node>
srvctl stop nodeapps –n <rac node>
srvctl status nodeapps –n <rac node>

Start / Stop a listener on a RAC node

srvctl start|stop listener -n node_name [-l listener_name_list]
e.g.
srvctl start listener -n node2
srvctl start listener -n node2 -l DATAGUARD_LISTENER
srvctl stop LISTENER_SCAN1

Start / Stop services on a RAC node

srvctl stop database command implicity does a srvctl stop services (because services are dependent on database).
However, a subsequent srvctl start database requires an explicit srvctl start service

• service name list is optional and if not provided, the SRVCTL starts all of the database's services
  
• -c connect_str Connect string (default: / as sysdba)
  
• -q Query connect string from standard input

srvctl start service -d <db_unique_name> [-s service_name_list [-i <inst_name>]]  [-o <start_options>] [-c connect_str | -q]
srvctl stop service -d db_unique_name [-s service_name_list [-i inst_name]]  [-c connect_str | -q] [-f]

Status of an ASM instance on a RAC node

srvctl status asm -n sdtcsynoda01-rac
srvctl status asm -n sdtcsynoda02-rac

Status of the database, all instances and all services

srvctl status database -d TSTEV3 -v

Instance TSTEV31 is running on node sdtcsynoda01-rac
Instance TSTEV32 is running on node sdtcsynoda02-rac

Status of named instances with their current services (if on local node)

srvctl status instance -d TSTEV3 -i TSTEV31 -v

Instance TSTEV31 is running on node sdtcsynoda01-rac. Instance status: Open.

srvctl status instance -d TSTEV3 -i TSTEV32 -v

Instance TSTEV32 is running on node sdtcsynoda02-rac with online services DOTS. Instance status: Open.

Add a new node

srvctl add nodeapps -n myclust-1 -o $ORACLE_HOME –A 139.184.201.1/255.255.255.0/hme0

Add a new database

srvctl add database -d ORACLE -o $ORACLE_HOME
eg.
srvctl add database -d MASTASPO -o /u01/app/oracle/product/12.1.0.2/dbhome_1 -r PHYSICAL_STANDBY -s MOUNT

Add named instances to an existing database

srvctl add instance -d ORACLE -i RAC01 -n myclust-1
srvctl add instance -d ORACLE -i RAC02 -n myclust-2
srvctl add instance -d ORACLE -i RAC03 -n myclust-3
eg.
srvctl add instance -d MASTASPO -i MASTASPO -n sdtcoda01-rac

Add a service to an existing database with preferred instances (-r) and available instances (-a). Use basic failover to the available instances

srvctl add service -d ORACLE -s STD_BATCH -r RAC01 -a RAC02

Add a service to an existing database with preferred instances (-r) and available instances (-a). Use preconnect at the available instances

srvctl add service -d ORACLE -s STD_BATCH -r RAC01 -a RAC02 -P PRECONNECT

Remove the applications for a database

srvctl remove database -d ORACLE

Remove the applications for named instances of an existing database

srvctl remove instance -d ORACLE -i RAC03
srvctl remove instance -d ORACLE -i RAC04

Remove the service

srvctl remove service -d ORACLE -s STD_BATCH

Remove the service from the instances

srvctl remove service -d ORACLE -s STD_BATCH -i RAC03,RAC04

Remove all node applications from a node

srvctl remove nodeapps -n myclust-4

Modify an instance to execute on another node

srvctl modify instance -d ORACLE -n myclust-4

Modify a service to execute on another node

srvctl modify service -d ORACLE -s HOT_BATCH -i RAC01 -t RAC02

Modify an instance to be a preferred instance for a service

srvctl modify service -d ORACLE -s HOT_BATCH -i RAC02 –r

Relocate a service from one instance to another

srvctl relocate service -d orac -s CRM -i RAC04 -t RAC01

Switchover / failover a database from one node (server) to another

srvctl relocate db -d orac -n server02

Enable CRS resources (resources can be up or down when these commands are issued)

Enable the database

srvctl enable database -d ORACLE

Enable the named instances

srvctl enable instance -d ORACLE -i RAC01, RAC02

Enable the service

srvctl enable service -d ORACLE -s ERP,CRM

Enable the service at the named instance

srvctl enable service -d ORACLE -s CRM -i RAC03

Disable CRS resources (resources must be down when these commands are issued)

Disable the database globally

srvctl disable database -d ORACLE

Disable the named instances

srvctl disable instance -d ORACLE -i RAC01, RAC02

Disable the service(s) globally

srvctl disable service -d ORACLE -s ERP,CRM

Disable the service on the named instance

srvctl disable service -d ORACLE -s CRM -i RAC02

Status of a named services

srvctl status service -d TSTEV3 -s DOTS -v

Status of all nodes supporting database applications

srvctl status nodeapps

How to tell if database is a RAC cluster

This will be TRUE if RAC database

show parameter cluster

or, the GV$ views will show more than 1 record

select * from gv$instance;

   INST_ID INSTANCE_NUMBER INSTANCE_NAME    HOST_NAME                                                        VERSION           STARTUP_T STATUS       PAR    THREAD# ARCHIVE LOG_SWITCH_WAIT LOGINS     SHU DATABASE_STATUS   INSTANCE_ROLE      ACTIVE_ST BLO     CON_ID INSTANCE_MO EDITION FAMILY
---------- --------------- ---------------- ---------------------------------------------------------------- ----------------- --------- ------------ --- ---------- ------- --------------- ---------- --- ----------------- ------------------ --------- --- ---------- ----------- ------- --------------------------------------------------------------------------------
         2               2 DEV32          oda02-rac                                                 12.1.0.2.0        20-JUL-16 OPEN         YES         2 STARTED                  ALLOWED    NO  ACTIVE            PRIMARY_INSTANCE   NORMAL    NO           0 REGULAR     EE
         1               1 DEV31          oda01-rac                                                 12.1.0.2.0        13-OCT-16 OPEN         YES         1 STARTED                  ALLOWED    NO  ACTIVE            PRIMARY_INSTANCE   NORMAL    NO           0 REGULAR     EE

2 rows selected.

or

set serverout on
begin
    if dbms_utility.is_cluster_database then
        dbms_output.put_line('Running in RAC mode.');
    else
        dbms_output.put_line('Running in EXCLUSIVE mode.');
    end if;
end;
/

or

select * from v_$active_instances;

or

select * from v_$thread;

Show session distribution across the RAC nodes

select inst_id
,      count(*) sessions
from   gv$session
where  type = 'USER'
group  by inst_id
/