Expensive All,
On this submit i’ve defined the step-by-step oracle 19C RAC startup sequence.
The startup
sequence in Oracle 19c RAC is complicated as a result of multi-instance, multi-node
nature of RAC.
1. Begin Oracle Grid Infrastructure
(Clusterware) – crsctl
2. Begin Oracle ASM (Computerized
Storage Administration) – srvctl / as half
of cluster begin
3. Begin Oracle RAC Database
Situations utilizing srvctl
4. Begin Oracle Web Listener
5. Begin Oracle Companies (non-compulsory)
6. Begin ASM (if not already achieved)
This
course of ensures that each one situations throughout nodes are correctly synchronized,
making certain excessive availability and information consistency in a shared-disk
setting like Oracle RAC. Correct startup ensures that each one Oracle processes,
database companies, and storage are appropriately initialized, offering a steady
setting to your functions and database customers.
Oracle 19c RAC Startup Sequence: Detailed
Rationalization
In Oracle
19c Actual Utility Clusters (RAC), the startup sequence refers to
the steps Oracle follows to carry the database and its related companies into
an operational state. The startup course of is completely different in a RAC setting
in comparison with a single-instance Oracle database as a result of it includes beginning and
coordinating a number of situations throughout a number of nodes, making certain they will work
collectively in a shared-disk setting.
The startup
sequence in Oracle RAC is split into the next levels:
1. Beginning Oracle Grid Infrastructure (CRS) and Cluster ware
Earlier than
any Oracle RAC database occasion begins, Oracle Cluster ware (Grid
Infrastructure) should be began on all nodes within the cluster.
1: Begin the Cluster ware Stack (CRS)
> Oracle Cluster ware manages the nodes within the
cluster and ensures they operate as a single logical unit. This consists of
monitoring the well being of all situations, offering failover mechanisms, and
managing assets like voting disks and OCR (Oracle Cluster
Registry).
> Cluster ware companies (CRS)
should be operating on every node to handle the cluster’s well being.
Instructions:
$ crsctl begin crs # Begin Oracle Clusterware (CRS) on all
nodes
Once you
problem this command, the next companies are began:
Clusterware Daemons: These embody crsd, evmd, and cssd.
crsd (Cluster Prepared Companies Daemon): Manages Oracle Clusterware assets.
evmd (Occasion Supervisor Daemon): Collects and processes occasions within the cluster
cssd (Cluster Synchronization Companies Daemon): Manages cluster membership and coordinates node standing and interconnect exercise.
Begin Oracle Clusterware (Oracle ASM)
> For those who’re utilizing Oracle
ASM (Computerized Storage Administration) to your RAC database, it should additionally
be began as a part of the Clusterware stack.
> ASM is liable for managing
the storage for Oracle databases in a RAC setting. ASM organizes information
into disk teams and offers striping and mirroring for prime
availability.
Instructions:
$ crsctl begin asm
This
command begins the ASM occasion, and it’ll mount the ASM disk teams
that comprise the Oracle database information, together with voting disks
and OCR (Oracle Cluster Registry).
Beginning
Oracle RAC Database Situations
As soon as Clusterware
is up and operating, the subsequent step is to begin the Oracle RAC database
situations. This step begins every occasion of the RAC database on every node
within the cluster.
>> Begin the Database Situations Utilizing srvctl
To start out
a database in Oracle RAC, you sometimes use the srvctl command. This command ensures that each one situations
of the RAC database are correctly began, making certain right inter-node
communication and Cache Fusion performance.
> srvctl mechanically begins all
required Oracle background processes, together with LGWR (Log Author), DBWn
(Database Author), and PMON (Course of Monitor), and ensures correct
interconnect exercise between nodes.
Instructions:
$ srvctl begin database -d
ex:
database that you just need to begin.
$srvctl begin database -d racsdb
2. Oracle Occasion Startup Sequence
As soon as the srvctl command is issued, Oracle begins the next
occasion startup sequence for every node within the cluster:
Course of Initialization:
> The occasion processes like SMON,
PMON, and others are began. These processes make sure the occasion runs
in a wholesome state.
Occasion Registration with the Listener:
> Every occasion registers itself
with the Oracle Web Listener for shopper connections. It ensures that the
listener is aware of which occasion is obtainable to service requests for that
specific occasion.
Shared Reminiscence Allocation:
>SGA (System World Space) and PGA (Program World Space)
are allotted for every occasion , SGA is a shared reminiscence area that
accommodates information and management info for the database.
> PGA is a non-public reminiscence area used
by Oracle background processes and consumer periods.
World Enqueue Initialization:
Oracle RAC makes use of a shared world
cache to handle locks and latches on information blocks throughout all nodes. The
situations talk and synchronize by way of World Enqueue Companies (GES)
and World Cache Companies (GCS).
> The World Cache layer
ensures consistency of information throughout RAC nodes.
Database Opening: After the occasion processes and
reminiscence buildings are initialized, the Database itself is opened. Oracle
opens the database in READ ONLY mode to make sure that it may be accessed
by all situations of the RAC database, and parallel execution is
obtainable throughout nodes.
>The redo log information are
opened to permit transaction processing.
Cache Fusion Initialization:
> Cache Fusion ensures that information blocks are
shared throughout situations. Oracle will provoke World Cache Synchronization
to synchronize the shared reminiscence buildings and information blocks between situations.
> That is key in Oracle RAC to
guarantee all nodes are per the information they share.
Database Processes Begin: Database processes, comparable to LGWR
(Log Author), DBWn (Database Author), SMON (System Monitor), and PMON
(Course of Monitor), are began. These processes are liable for sustaining
the well being of the database and managing transactional and background
operations.
Confirm
Database Occasion Startup
You possibly can
confirm the standing of your RAC database situations and be sure that they’re up
and operating with the next command:
$ srvctl standing database -d
The
output will point out which situations are operating and their standing throughout all
RAC nodes.
3. Beginning Oracle Web Listener
The Oracle
Web Listener is a course of that listens for incoming shopper connection
requests and directs these requests to the suitable database occasion within the
cluster.
Begin Oracle Listener
Use the srvctl utility to begin the listener for Oracle RAC:
Instructions:
$ srvctl begin listener -l
This
command begins the listener to your Oracle RAC database, permitting shopper
connections to be established.
4. Begin Oracle Companies — Elective
Oracle
companies can help you handle the load balancing and excessive availability of the
database in a RAC setting. For instance, Oracle can use Service Names
to direct shoppers to the suitable occasion primarily based on load or availability.
Begin Oracle
Companies Utilizing srvctl
$ srvctl begin service -d
This
command begins the desired service on the obtainable situations. In a RAC
setup, Oracle can configure companies to run on particular nodes or throughout all
nodes within the cluster.
Confirm Service Standing
To examine
the standing of the companies, you should use the next command:
$ srvctl standing service -d
5. Beginning Oracle Computerized Storage Administration
(ASM)
ASM
(Computerized Storage Administration) is liable for managing database storage in
RAC environments. It must be began to handle disk teams and deal with file
operations.
Step 1: Begin ASM Utilizing srvctl
You possibly can
begin ASM utilizing the srvctl command
as follows:
$ srvctl begin/standing/cease asm
6. Database and Occasion Synchronization in RAC
As soon as all
situations are up, and the Oracle Grid Infrastructure is operating, Oracle
RAC ensures that each one situations are synchronized by way of Cache Fusion. This
synchronization permits a number of situations to entry the identical set of database
information (e.g., information information, management information, and redo log information) in a shared storage
configuration.
Monitor Cluster Synchronization
You possibly can
monitor Cache Fusion efficiency utilizing the v$gc_stats view:
crsctl
examine ctss
crsctl
examine css
crsctl
examine cluster
methods to
examine cache fusion in Oracle RAC:
GCS
statistics: GCS
statistics for present and cr blocks, comparable to gc present blocks acquired and gc
cr blocks acquired, can be utilized to investigate the impact of cache fusion.
GCS wait
occasions: GCS
wait occasions, comparable to gc present block 3-way and gc cr grant
2-way, can be utilized to investigate the impact of cache fusion.
V$SYSSTAT
view: The V$SYSSTAT view will be queried to observe world cache statistics.
Cache Fusion is a characteristic in
Oracle RAC that permits a number of situations to share and browse the identical information block
concurrently. It makes use of the World Cache Service (GCS) to examine if one other
occasion has a duplicate of a knowledge block earlier than accessing it. If one other
occasion has the block, Cache Fusion transfers it straight between the
situations with out writing it to disk
