IPADDRESS DETAILS

There are three ranges of IPv4 addresses reserved for private use:

10.0.0.0/8: This range includes all IP addresses from 10.0.0.0 to 10.255.255.255, 

allowing for over 16 million unique addresses. It is commonly used in larger networks, 

such as corporate intranets.

172.16.0.0/12: This range includes all IP addresses from 172.16.0.0 to 172.31.255.255, 

providing around 1 million unique addresses. It is often used by medium-sized organizations 

or for network segmentation within larger networks.

192.168.0.0/16: This range includes all IP addresses from 192.168.0.0 to 192.168.255.255, 

allowing for over 65,000 unique addresses. It is widely used in home networks and small to 

medium-sized businesses due to its simplicity and ease of use.

IP addresses are identifiers for devices in computer networks.

IPv4 addresses are 32-bit numerical addresses written in four decimal numbers separated by periods.

IPv6 addresses are 128-bit hexadecimal addresses written in eight groups of four hexadecimal digits separated by colons.

Public IP addresses are globally unique and directly accessible from the internet.

Private IP addresses are used within private networks like LANs and intranets and are not directly accessible from the internet.

Private IP address ranges include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, defined in RFC 1918.

Static IP addresses are manually configured and remain constant over time.

Dynamic IP addresses are automatically assigned by DHCP servers and may change over time.

Reserved IP addresses are set aside for specific purposes such as multicast, loopback, or broadcast communications.

Golden gate 19c all in one approach

 

GGSCI> info extract extract_name, showch ;

copy the SCN number from above output. 

select name, thread#, sequence#, status, first_time, next_time, first_change#, next_change# from  v$archived_log where 25772732953522 between first_change# and next_change#;

select name, thread#, sequence#, status, first_time, next_time, first_change#, next_change# from  v$archived_log where <scn> between first_change# and next_change#;

Path/to/archivelog/1_8322558_956503891.arc

Linux

systemctl start service_name

systemctl stop service_name

systemctl enable service_name

systemctl disable service_name

systemctl status service_name

sudo chkconfig service_name on

sudo chkconfig service_name off

sudo chkconfig service_name status

bash --noprofile --norc starts a completely clean, bare-bones Bash shell without running any of your normal startup scripts.

---

What it does

When you start Bash normally, it loads several configuration files, such as:

• /etc/profile → system-wide environment variables

• ~/.bash_profile, ~/.bash_login, ~/.profile → user login scripts

• ~/.bashrc → aliases, functions, prompt settings, etc.

These can set your PATH, prompt, aliases, etc.
Sometimes you don’t want that — especially when testing or running untrusted scripts.

The flags:

• --noprofile → skip /etc/profile and any personal profile files.

• --norc → skip reading ~/.bashrc.

Errors while running "yum update or dnf update" :- Errors during downloading metadata for repository 'pgdg-common':

 PostgreSQL common RPMs for RHEL / Rocky 8 - x86_64                                                                          353  B/s | 659  B     00:01

PostgreSQL common RPMs for RHEL / Rocky 8 - x86_64                                                                          0.0  B/s |   0  B     00:00

Errors during downloading metadata for repository 'pgdg-common':

  - Curl error (37): Couldn't read a file:// file for file:///etc/pki/rpm-gpg/RPM-GPG-KEY-PGDG [Couldn't open file /etc/pki/rpm-gpg/RPM-GPG-KEY-PGDG]

Error: Failed to retrieve GPG key for repo 'pgdg-common': Curl error (37): Couldn't read a file:// file for file:///etc/pki/rpm-gpg/RPM-GPG-KEY-PGDG [Couldn't open file /etc/pki/rpm-gpg/RPM-GPG-KEY-PGDG]

[oracle@pm ~]$ cd /etc/yum.repos.d/

sudo rm pg* 

-- Note :- just remove the package which having error as above and then you're good to go --

# mkdir /var/lib/rpm/backup
# cp -a /var/lib/rpm/__db* /var/lib/rpm/backup/
# rm -f /var/lib/rpm/__db.[0-9][0-9]*
# rpm --quiet -qa
# rpm --rebuilddb
# yum clean all

Triggers in oracle

 -- Creating a table for demonstration purposes

CREATE TABLE your_table (

    id NUMBER PRIMARY KEY,

    data VARCHAR2(50),

    last_updated TIMESTAMP

);

-- BEFORE INSERT Trigger

CREATE OR REPLACE TRIGGER before_insert_trigger

BEFORE INSERT ON your_table

FOR EACH ROW

BEGIN

    -- Code to be executed before insert

    -- For example, setting a default value

    :NEW.last_updated := SYSTIMESTAMP;

END;

/

-- AFTER INSERT Trigger

CREATE OR REPLACE TRIGGER after_insert_trigger

AFTER INSERT ON your_table

FOR EACH ROW

BEGIN

    -- Code to be executed after insert

    -- For example, logging the insertion

    INSERT INTO log_table (log_message) VALUES ('New row inserted');

END;

/

-- BEFORE UPDATE Trigger

CREATE OR REPLACE TRIGGER before_update_trigger

BEFORE UPDATE ON your_table

FOR EACH ROW

BEGIN

    -- Code to be executed before update

    -- For example, preventing updates under certain conditions

    IF :NEW.data = 'restricted' THEN

        RAISE_APPLICATION_ERROR(-20001, 'Updates to "restricted" data are not allowed.');

    END IF;

END;

/

-- AFTER UPDATE Trigger

CREATE OR REPLACE TRIGGER after_update_trigger

AFTER UPDATE ON your_table

FOR EACH ROW

BEGIN

    -- Code to be executed after update

    -- For example, updating related records in another table

    UPDATE related_table

    SET related_data = :NEW.data

    WHERE related_id = :NEW.id;

END;

/

-- BEFORE DELETE Trigger

CREATE OR REPLACE TRIGGER before_delete_trigger

BEFORE DELETE ON your_table

FOR EACH ROW

BEGIN

    -- Code to be executed before delete

    -- For example, preventing deletion of specific records

    IF :OLD.data = 'protected' THEN

        RAISE_APPLICATION_ERROR(-20002, 'Deletion of "protected" records is not allowed.');

    END IF;

END;

/

-- AFTER DELETE Trigger

CREATE OR REPLACE TRIGGER after_delete_trigger

AFTER DELETE ON your_table

FOR EACH ROW

BEGIN

    -- Code to be executed after delete

    -- For example, logging the deletion

    INSERT INTO log_table (log_message) VALUES ('Row deleted');

END;

/

GRANT & REVOKE Commands for the new_user on Oracle 19c Database ?

---------- Grant Commands ------------

GRANT CREATE CLUSTER, CREATE ANY CLUSTER, ALTER ANY CLUSTER, DROP ANY CLUSTER TO &new_user;
GRANT ALTER DATABASE, ALTER SYSTEM, AUDIT SYSTEM TO &new_user;
GRANT CREATE ANY INDEX, ALTER ANY INDEX, DROP ANY INDEX TO &new_user;
GRANT CREATE PROFILE, ALTER PROFILE, DROP PROFILE TO &new_user;
GRANT CREATE ROLE, ALTER ANY ROLE, DROP ANY ROLE, GRANT ANY ROLE TO &new_user;
GRANT CREATE ROLLBACK SEGMENT, ALTER ROLLBACK SEGMENT, DROP ROLLBACK SEGMENT TO &new_user;
GRANT CREATE USER, ALTER USER, DROP USER, CREATE SESSION TO &new_user;
GRANT CREATE VIEW, CREATE ANY VIEW, DROP ANY VIEW TO &new_user;
GRANT CREATE SYNONYM, CREATE ANY SYNONYM, CREATE PUBLIC SYNONYM, DROP ANY SYNONYM, DROP PUBLIC SYNONYM TO &new_user;
GRANT CREATE SESSION, ALTER SESSION, RESTRICTED SESSION, ALTER RESOURCE COST TO &new_user;
GRANT CREATE TABLE, CREATE ANY TABLE, ALTER ANY TABLE, DROP ANY TABLE, SELECT ANY TABLE, INSERT ANY TABLE, UPDATE ANY TABLE, DELETE ANY TABLE, LOCK ANY TABLE TO &new_user;
GRANT CREATE TABLESPACE, ALTER TABLESPACE, DROP TABLESPACE, MANAGE TABLESPACE TO &new_user;

----- Revoke Commands -----

REVOKE CREATE CLUSTER, CREATE ANY CLUSTER, ALTER ANY CLUSTER, DROP ANY CLUSTER FROM &new_user;

REVOKE ALTER DATABASE, ALTER SYSTEM, AUDIT SYSTEM FROM &new_user;

REVOKE CREATE ANY INDEX, ALTER ANY INDEX, DROP ANY INDEX FROM &new_user;

REVOKE CREATE PROFILE, ALTER PROFILE, DROP PROFILE FROM &new_user;

REVOKE CREATE ROLE, ALTER ANY ROLE, DROP ANY ROLE, GRANT ANY ROLE FROM &new_user;

REVOKE CREATE ROLLBACK SEGMENT, ALTER ROLLBACK SEGMENT, DROP ROLLBACK SEGMENT FROM &new_user;

REVOKE CREATE USER, ALTER USER, DROP USER, CREATE SESSION FROM &new_user;

REVOKE CREATE VIEW, CREATE ANY VIEW, DROP ANY VIEW FROM &new_user;

REVOKE CREATE SYNONYM, CREATE ANY SYNONYM, CREATE PUBLIC SYNONYM, DROP ANY SYNONYM, DROP PUBLIC SYNONYM FROM &new_user;

REVOKE CREATE SESSION, ALTER SESSION, RESTRICTED SESSION, ALTER RESOURCE COST FROM &new_user;

REVOKE CREATE TABLE, CREATE ANY TABLE, ALTER ANY TABLE, DROP ANY TABLE, SELECT ANY TABLE, INSERT ANY TABLE, UPDATE ANY TABLE, DELETE ANY TABLE, LOCK ANY TABLE FROM &new_user;

REVOKE CREATE TABLESPACE, ALTER TABLESPACE, DROP TABLESPACE, MANAGE TABLESPACE FROM &new_user;

ALTER USER &new_user QUOTA 100M ON &tablespace;

GRANT UNLIMITED TABLESPACE TO &new_user;

Oracle 19c Architecture Explanation ?

Library cache:-

stores SQL and PL/SQL statements along with their execution plans.

Data Dictionary Cache:-

stores info about database schema such as tables, columns, definitions, indexes, privileges. 

Shared Pool:-

shared memory structures for SQL and PL/SQL execution.

it contains frequently executed SQL statements, execution plans, data dictionary information.

--

buffer memory :- i/o operations happen.

cache memory :- read/write operations happen.

filesystem handling in Oracle 19c RAC ?

 1. verify ACFS installation.

2. Create an ACFS File System:-

srvctl add filesystem -d <device> -m <mount_point>

eg. srvctl add filesystem -d /dev/asm/acfs-vol1-123 -m /acfs_file

3. Start the ACFS File System:-

srvctl start filesystem -d <device>

eg. srvctl start filesystem -d /dev/asm/acfs-vol1-123

4. Mount the ACFS File System:

mount -t acfs <device> <mount_point>

eg. mount -t acfs /dev/asm/acfs-vol1-123 /acfs_file

5. Verify ACFS Status:

srvctl status filesystem -d <device>

eg. srvctl status filesystem -d /dev/asm/acfs-vol1-123

6. Resize ACFS File System :-

acfsutil size +<size> <mount_point>

eg. acfsutil size +100G /acfs_file 

7. List all ACFS file systems:

acfsutil info fs

8. Display information about a specific ACFS file system:

acfsutil info fs -o volume <mount_point>

eg. acfsutil info fs -o volume  /acfs_file

9. Stop  an ACFS FILE SYSTEM:

srvctl stop filesystem -d <device>

eg. srvctl stop filesystem -d /dev/asm/acfs-vol1-123

10. Remove an ACFS file system:

srvctl remove filesystem -d <device>

eg. srvctl remove filesystem -d /dev/asm/acfs-vol1-123

11. Display ACFS resource dependency:

srvctl config fs -d <device>

eg. srvctl config fs -d /dev/asm/acfs-vol1-123

12. 

optimizer parameters in oracle 19c db

begin

for x in (select name from v$parameter where name like 'optimizer%')

loop

dbms_output.put_line(x.name);

end loop;

end;

-------------------------------------------------------
optimizer_features_enable
optimizer_mode
optimizer_index_cost_adj
optimizer_index_caching
optimizer_dynamic_sampling
optimizer_ignore_hints
optimizer_secure_view_merging
optimizer_use_pending_statistics
optimizer_capture_sql_plan_baselines
optimizer_use_sql_plan_baselines
optimizer_use_invisible_indexes
optimizer_adaptive_reporting_only
optimizer_adaptive_plans
optimizer_inmemory_aware
optimizer_adaptive_statistics
optimizer_ignore_parallel_hints

----------------------------------------------------------

-- Enable timing of SQL statements

SET TIMING ON;

-- Enable autotrace for detailed execution plans

SET AUTOTRACE ON;

-- Set the threshold for identifying slow queries (adjust as needed)

ALTER SESSION SET STATISTICS_LEVEL = ALL;

ALTER SESSION SET TIMED_STATISTICS = TRUE;

ALTER SESSION SET SQL_TRACE = TRUE;

-- Your SQL query goes here

SELECT *

FROM your_table

WHERE your_condition;

-- Reset session settings

ALTER SESSION SET STATISTICS_LEVEL = TYPICAL;

ALTER SESSION SET TIMED_STATISTICS = FALSE;

ALTER SESSION SET SQL_TRACE = FALSE;

-- Disable timing of SQL statements

SET TIMING OFF;

-- Display execution plan

-- Uncomment the line below if you want to see the execution plan

-- SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'ALLSTATS LAST'));

> /dev/null 2>&1 to prevent errors

> /dev/null : Redirects standard output to /dev/null, discarding it.

2>&1 : Redirects standard error to the same location as standard output. This ensures that both

standard output and standard error are discarded.

script.sh > script.log 2>&1

to prevent errors :-

command or script > /dev/null 2>&1

echo -e "something" > filename enable backlash escape

 echo -e "india\nmaharashtra" > india.txt

cat india.txt

india

maharashtra