• DBMS_OUTPUT
• UTL_FILE
• UTL_MAIL
• UTL MAIL
• DBMS_ALERT
• DBMS_LOCK
• DBMS_SESSION
• DBMS APPLICATION INFO
• HTP
• DBMS_SCHEDULER
Tuesday, December 31, 2024
Tuesday, September 10, 2024
ORA-03113: end-of-file on communication channel
SQL> startup
ORACLE instance started.
Total System Global Area 4294964000 bytes
Fixed Size 9143072 bytes
Variable Size 1577058304 bytes
Database Buffers 2701131776 bytes
Redo Buffers 7630848 bytes
Database mounted.
ORA-03113: end-of-file on communication channel
Process ID: 46641
Session ID: 259 Serial number: 54397
SQL> STARTUP MOUNT;
SP2-0642: SQL*Plus internal error state 2133, context 3114:0:0
Unsafe to proceed
ORA-03114: not connected to ORACLE
SQL> sqlplus
SP2-0042: unknown command "sqlplus" - rest of line ignored.
SQL>
SQL>
SQL>
SQL> exit
Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
[oracle@vmi2001271 ~]$ sqlplus
SQL*Plus: Release 19.0.0.0.0 - Production on Tue Sep 10 09:15:03 2024
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle. All rights reserved.
Enter user-name: sys as sysdba
Enter password:
Connected to an idle instance.
SQL> SHUTDOWN IMMEDIATE;
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Additional information: 4376
Additional information: -896098569
Process ID: 0
Session ID: 0 Serial number: 0
SQL> shutdown abort
ORACLE instance shut down.
SQL> STARTUP MOUNT;
ORACLE instance started.
Total System Global Area 4294964000 bytes
Fixed Size 9143072 bytes
Variable Size 1577058304 bytes
Database Buffers 2701131776 bytes
Redo Buffers 7630848 bytes
Database mounted.
SQL> ^C
SQL> startup nomount
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL> alter database clear unarchived logfile group 3;
Database altered.
SQL> alter database clear unarchived logfile group 2;
Database altered.
SQL> alter database clear unarchived logfile group 1;
Database altered.
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 4294964000 bytes
Fixed Size 9143072 bytes
Variable Size 1577058304 bytes
Database Buffers 2701131776 bytes
Redo Buffers 7630848 bytes
Database mounted.
Database opened.
Tuesday, July 2, 2024
CV Design Using PLSQL Dynamic Content
declare
cursor c_emp is
SELECT j.Emp_reg_id,
(p.First_name || ' ' || p.last_name) Name,
p.father_name,
p.mother_name,
p.Address,
p.Phone,
p.email,
p.date_of_birth,
p.religion,
p.blood_group,
p.Nationality
FROM job_seeker_registration j
JOIN Personal_details p ON j.emp_reg_id = p.emp_reg_id
WHERE j.emp_reg_id = :G_EMP_ID;
cursor c_academic_details is
SELECT
a.Name_of_degree,
a.Subject,
a.Name_of_institute,
a.Duration,
a.result
FROM academic_details a
WHERE a.emp_reg_id = :G_EMP_ID;
--
cursor c_experience is
SELECT
e.job_title,
e.dept_name,
to_number(ROUND((e.End_date - e.Start_date) / 365)) Year_Of_Experience
FROM experience_details e
WHERE e.emp_reg_id= :G_EMP_ID;
---
cursor c_skills is SELECT
s.Skill_name,
s.skill_level
FROM skills s
WHERE s.emp_reg_id= :G_EMP_ID;
---
cursor c_references is SELECT
r.Reference_name,
r.Designation,
r.contact_no
FROM REFERENCES r
WHERE r.emp_reg_id= :G_EMP_ID;
begin
for rec in c_emp loop
htp.p('<div style="border: 1px solid #000; padding: 20px; margin-bottom: 20px; font-family: Arial, sans-serif;">');
htp.p('<h1 style="text-align: center;padding:0%;">Curiculam Vitae Of</h1>');
htp.p('<h2 style="text-align: center;padding:0%;">' || rec.Name || '</h2>');
htp.p('<h4 style="text-align: center;padding:0%;"><strong>Address:</strong> ' || rec.Address || '</h4>');
htp.p('<h4 style="text-align: center;padding:0%;"><strong>Phone:</strong> ' || rec.Phone || '</h4>');
htp.p('<h4 style="text-align: center;padding:0%;"><strong>Email:</strong> ' || rec.email || '</h4>');
htp.p('<h2>Personal Information</h2>');
htp.p('<p><strong>Father Name:</strong> ' || rec.father_name || '</p>');
htp.p('<p><strong>Mother Name:</strong> ' || rec.mother_name || '</p>');
htp.p('<p><strong>Address:</strong> ' || rec.Address || '</p>');
htp.p('<p><strong>Phone:</strong> ' || rec.Phone || '</p>');
htp.p('<p><strong>Email:</strong> ' || rec.email || '</p>');
htp.p('<p><strong>Date of Birth:</strong> ' || rec.date_of_birth || '</p>');
htp.p('<p><strong>Religion:</strong> ' || rec.religion || '</p>');
htp.p('<p><strong>Blood Group:</strong> ' || rec.blood_group || '</p>');
htp.p('<p><strong>Nationality:</strong> ' || rec.Nationality || '</p>');
end loop;
begin
--academic
htp.p('<h2>Academic Details</h2>');
htp.p('<table border="1" style="width: 100%; border-collapse: collapse;">');
htp.p('<tr><th>Degree</th><th>Subject</th><th>Institute</th><th>Duration</th><th>Result</th></tr>');
for rec_academi in c_academic_details loop
htp.p('<tr>');
htp.p('<td>' || rec_academi.Name_of_degree || '</td>');
htp.p('<td>' || rec_academi.Subject || '</td>');
htp.p('<td>' || rec_academi.Name_of_institute || '</td>');
htp.p('<td>' || rec_academi.Duration || '</td>');
htp.p('<td>' || rec_academi.result || '</td>');
htp.p('</tr>');
end loop;
htp.p('</table>');
--Experiences
htp.p('<h2>Experience Details</h2>');
htp.p('<table border="1" style="width: 100%; border-collapse: collapse;">');
htp.p('<tr><th>Job Title</th><th>Department</th><th>Years of Experience</th></tr>');
for rec_experience in c_experience loop
htp.p('<tr>');
htp.p('<td>' || rec_experience.job_title || '</td>');
htp.p('<td>' || rec_experience.dept_name || '</td>');
htp.p('<td>' || rec_experience.Year_Of_Experience || '</td>');
htp.p('</tr>');
htp.p('</table>');
end loop;
--SKILLS
htp.p('<h2>Skills</h2>');
htp.p('<table border="1" style="width: 100%; border-collapse: collapse;">');
htp.p('<tr><th>Skill Name</th><th>Skill Level</th></tr>');
for rec_skills in c_skills
Loop
htp.p('<tr>');
htp.p('<td>' || rec_skills.skill_name || '</td>');
htp.p('<td>' || rec_skills.skill_level || '</td>');
htp.p('</tr>');
htp.p('</table>');
end loop;
---REFERENCES
htp.p('<h2>References</h2>');
htp.p('<table border="1" style="width: 100%; border-collapse: collapse;">');
htp.p('<tr><th>Name</th><th>Designation</th><th>Contact No</th></tr>');
htp.p('<tr>');
for rec_references in c_references
loop
htp.p('<tr>');
htp.p('<td>' || rec_references.Reference_name || '</td>');
htp.p('<td>' || rec_references.Designation || '</td>');
htp.p('<td>' || rec_references.contact_no || '</td>');
htp.p('</tr>');
htp.p('</table>');
end loop;
htp.p('</table>');
htp.p('</div>');
end;
end;
Sunday, May 19, 2024
Algorithms to Live By: The Computer Science of Human Decisions
Algorithms to Live By: The Computer Science of Human Decisions
In this excellent book, Brian Christian and Tom Griffiths, explain how regular people use algorithms without even realizing it in their day-to-day lives, and how we can learn from computer science to make better decisions in various aspects of our lives, from finding a spouse to finding a parking spot, from organizing our inbox to peering into the future. Here are seven, eye-opening and powerful lessons from the book that I hope will intrigue you:
1. Optimal Stopping:
The book teaches us how to decide when to stop looking for something and settle for the best option we have found so far, whether it is a house, a job, or a partner. The book reveals the surprising mathematical formula that can help us maximize our chances of finding the optimal choice, and why it is sometimes better to act sooner rather than later.
2. Explore/Exploit:
The book shows us how to balance the trade-off between exploring new possibilities and exploiting existing ones, whether it is trying a new restaurant, reading a new book, or sticking to our favorites. The book explains the different strategies that can help us optimize our happiness, and why sometimes randomness can be the best policy.
3. Sorting:
The book demonstrates how to sort and organize our data and information, whether it is our email inbox, our closet, or our bookshelf. The book reveals the different algorithms that can help us sort things faster, easier, and more efficiently, and why sometimes messiness can be a virtue.
4. Caching:
The book illustrates how to manage our limited memory and attention, whether it is our computer's RAM, our brain's working memory, or our smartphone's notifications. The book reveals the different algorithms that can help us decide what to keep, what to discard, and what to retrieve, and why sometimes forgetting can be a blessing.
5. Scheduling:
The book instructs us how to schedule our tasks and activities, whether it is our to-do list, our calendar, or our meetings. The book reveals the different algorithms that can help us prioritize, allocate, and execute our work, and why sometimes procrastination can be a good thing.
6.Bayesian Reasoning:
The book guides us how to update our beliefs and opinions, whether it is our political views, our medical diagnosis, or our personal preferences. The book reveals the different algorithms that can help us incorporate new evidence, weigh probabilities, and make predictions, and why sometimes intuition can be misleading.
7. Networking:
The book advises us how to interact with others and cooperate, whether it is our family, our friends, or our colleagues. The book reveals the different algorithms that can help us negotiate, collaborate, and compete, and why sometimes altruism can be the best strategy.
I hope you enjoyed reading my review of this excellent book, and that it piqued your interest and curiosity to dive into the pages of the book. I highly recommend you satisfy your curiosity by picking this book up!
BOOK: https://amzn.to/3wCN9gz
You can get the audiobook for FREE by using the same link above when you register on the Audible platform.
Friday, May 10, 2024
How to Export Pluggable database specific user or schema
C:\export--directory name,manually build in a folder as your wish.
go to cmd as administrator mode.
connect to sys
alter session set container=orclpdb;
create directory exp_schema as 'C:\export';
GRANT read,write on DIRECTORY exp_schema TO SAMITY;
GRANT DATAPUMP_EXP_FULL_DATABASE TO samity;
expdp samity/samity@//107.167.94.211:1521/orclpdb DIRECTORY=exp_schema DUMPFILE=samitydb110524.dmp LOGFILE=samity_lg.log SCHEMAS=samity
Monday, May 6, 2024
Oracle 19c Install on Centos 7
--First connect the root
user name :root
password: your root password
--Now check the Machine Ram
grep MemTotal /proc/meminfo
--Check the Swap Space
grep SwapTotal /proc/meminfo
How to create a swap space on Linux or Centos 7
Introduction
One of the easiest ways to make your server more responsive, and guard against out-of-memory errors in your application, is to add some swap space. Swap is an area on a storage drive where the operating system can temporarily store data that it can no longer hold in memory.
This gives you the ability to increase the amount of information that your server can keep in its working memory, with some caveats. Reading from and writing to swap is slower than using memory, but it can provide a good safety net for when your server is low on memory.
Without swap, a server that runs out of memory may start killing applications to free up memory, or even crash. This can cause you to lose unsaved data or experience downtime. To ensure reliable data access, some applications require swap to function.
In this guide, we will cover how to create and enable a swap file on a CentOS 7 server.
Note
Although swap is generally recommended for systems utilizing traditional spinning hard drives, using swap with SSDs can cause issues with hardware degradation over time. Due to this consideration, we do not recommend enabling swap on DigitalOcean or any other provider that utilizes SSD storage. Doing so can impact the reliability of the underlying hardware for you and your neighbors.
If you need to improve the performance of your server, we recommend upgrading your Droplet. This will lead to better results in general and will decrease the likelihood of contributing to hardware issues that can affect your service.
Prerequisites
Before you begin with this guide, there are a few steps that need to be completed first.
You will need a CentOS 7 server installed and configured with a non-root user that has sudo privileges. If you haven’t done this yet, you can run through steps 1-4 in the CentOS 7 initial server setup guide to create this account.
Once you have your non-root user, you can use it to SSH into your CentOS server and continue with the installation of your swap file.
Check the System for Swap Information
Before we begin, we should take a look at our server’s storage to see if we already have some swap space available. While we can have multiple swap files or swap partitions, one should generally be enough.
We can see if the system has any configured swap by using swapon, a general-purpose swap utility. With the -s flag, swapon will display a summary of swap usage and availability on our storage device:
swapon -s
If nothing is returned by the command, then the summary was empty and no swap file exists.
Another way of checking for swap space is with the free utility, which shows us the system’s overall memory usage. We can see our current memory and swap usage (in megabytes) by typing:
free -m
total used free shared buffers cached
Mem: 3953 315 3637 8 11 107
-/+ buffers/cache: 196 3756
Swap: 0 0 4095
As you can see, our total swap space in the system is 0. This matches what we saw with swapon.
Check Available Storage Space
The typical way of allocating space for swap is to use a separate partition that is dedicated to the task. However, altering the partition scheme is not always possible due to hardware or software constraints. Fortunately, we can just as easily create a swap file that resides on an existing partition.
Before we do this, we should be aware of our current drive usage. We can get this information by typing:
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 59G 1.5G 55G 3% /
devtmpfs 2.0G 0 2.0G 0% /dev
tmpfs 2.0G 0 2.0G 0% /dev/shm
tmpfs 2.0G 8.3M 2.0G 1% /run
tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup
Note: the -h flag simply tells dh to output drive information in a human-friendly reading format. For example, instead of outputting the raw number of memory blocks in a partition, df -h will tell us the space usage and availability in M (for megabytes) or G (for gigabytes).
As you can see on the first line, our storage partition has 59 gigabytes available, so we have quite a bit of space to work with. Keep in mind that this is on a fresh, medium-sized VPS instance, so your actual usage might be very different.
Although there are many opinions about the appropriate size of a swap space, it really depends on your application requirements and your personal preferences. Generally, an amount equal to or double the amount of memory on your system is a good starting point.
Since my system has 4 gigabytes of memory, and doubling that would take a larger chunk from my storage space than I am willing to part with, I will create a swap space of 4 gigabytes to match my system’s memory.
Create a Swap File
Now that we know our available storage space, we can go about creating a swap file within our filesystem. We will create a file called swapfile in our root (/) directory, though you can name the file something else if you prefer. The file must allocate the amount of space that we want for our swap file, and it should be created in one contiguous block.
The best way to do this is to use the dd utility. This command will create a 4 gigabyte file:
sudo dd if=/dev/zero of=/swapfile count=4096 bs=1MiB
After entering your password to authorize sudo privileges, the swap file will be created. This can take a few moments, then the prompt will be returned to you. We can verify that the correct amount of space was reserved for swap by using ls:
ls -lh /swapfile
-rw-r--r-- 1 root root 4.0G Oct 30 11:00 /swapfile
As you can see, our swap file was created with the correct amount of space set aside.
Enable a Swap File
Right now, our file is created, but our system does not know that this is supposed to be used for swap. We need to tell our system to format this file as swap and then enable it.
Before we do that, we should adjust the permissions on our swap file so that it isn’t readable by anyone besides the root account. Allowing other users to read or write to this file would be a huge security risk. We can lock down the permissions with chmod:
sudo chmod 600 /swapfile
This will restrict both read and write permissions to the root account only. We can verify that the swap file has the correct permissions by using ls -lh again:
ls -lh /swapfile
-rw------- 1 root root 4.0G Oct 30 11:00 /swapfile
Now that our swap file is more secure, we can tell our system to set up the swap space for use by typing:
sudo mkswap /swapfile
Setting up swapspace version 1, size = 4194300 KiB
no label, UUID=b99230bb-21af-47bc-8c37-de41129c39bf
Our swap file is now ready to be used as a swap space. We can begin using it by typing:
sudo swapon /swapfile
To verify that the procedure was successful, we can check whether our system reports swap space now:
swapon -s
Filename Type Size Used Priority
/swapfile file 4194300 0 -1
This output confirms that we have a new swap file. We can use the free utility again to corroborate our findings:
free -m
total used free shared buffers cached
Mem: 3953 315 3637 8 11 107
-/+ buffers/cache: 196 3756
Swap: 4095 0 4095
Our swap has been set up successfully, and our operating system will begin to use it as needed.
Make the Swap File Permanent
Our swap file is enabled at the moment, but when we reboot, the server will not automatically enable the file for use. We can change that by modifying the fstab file, which is a table that manages filesystems and partitions.
Edit the file with sudo privileges in your text editor:
sudo nano /etc/fstab
At the bottom of the file, you need to add a line that will tell the operating system to automatically use the swap file that you created:
/swapfile swap swap sw 0 0
When you are finished adding the line, you can save and close the file. The server will check this file on each bootup, so the swap file will be ready for use from now on.
Tweak Your Swap Settings (Optional)
There are a few options that you can configure that will have an impact on your system’s performance when dealing with swap. These configurations are optional in most cases, and the changes that you make will depend on your application needs and your personal preference.
Swappiness
The swappiness parameter determines how often your system swaps data out of memory to the swap space. This is a value between 0 and 100 that represents the percentage of memory usage that will trigger the use of swap.
With values close to zero, the system will not swap data to the drive unless absolutely necessary. Remember, interactions with the swap file are “expensive” in that they are a lot slower than interactions with memory, and this difference in read and write speed can cause a significant reduction in an application’s performance. Telling the system not to rely on the swap as much will generally make your system faster.
Values that are closer to 100 will try to put more data into swap in an effort to keep more memory free. Depending on your applications’ memory profile, or what you are using your server for, this might be the better choice in some cases.
We can see the current swappiness value by reading the swappiness configuration file:
cat /proc/sys/vm/swappiness
30
CentOS 7 defaults to a swappiness setting of 30, which is a fair middle ground for most desktops and local servers. For a VPS system, we’d probably want to move it closer to 0.
We can set the swappiness to a different value by using the sysctl command. For instance, to set the swappiness to 10, we could type:
sudo sysctl vm.swappiness=10
vm.swappiness = 10
This setting will persist until the next reboot. To make the setting persist between reboots, we can add the outputted line to our sysctl configuration file:
sudo nano /etc/sysctl.conf
Add your swappiness setting to the bottom of the file:
vm.swappiness = 10
When you are finished adding the line, you can save and close the file. The server will now automatically set the swappiness to the value you declared on each bootup.
Cache Pressure
Another related value that you might want to modify is the vfs_cache_pressure. This setting affects the storage of special filesystem metadata entries. Constantly reading and refreshing this information is generally very costly, so storing it on the cache for longer is excellent for your system’s performance.
You can see the current value of this cache pressure by querying the proc filesystem again:
cat /proc/sys/vm/vfs_cache_pressure
100
As it is currently configured, our system removes inode information from the cache far too quickly. We can set this to a more conservative setting, like 50, by using sysctl:
sudo sysctl vm.vfs_cache_pressure=50
vm.vfs_cache_pressure = 50
Again, this is only valid for our current session. We can change that by adding it to our configuration file, like we did with our swappiness setting:
sudo nano /etc/sysctl.conf
At the bottom, add the line that specifies your new value:
vm.vfs_cache_pressure = 50
When you are finished adding the line, you can save and close the file. The server will now automatically set the cache pressure to the value you declared on each bootup.
Conclusion
By following the steps in this guide, you will have given your server some breathing room in terms of memory usage. Swap space is incredibly useful in avoiding some common problems.
If you are running into OOM (out of memory) errors, or if you find that your system is unable to use the applications that you need, the best solution is to optimize your application configurations or upgrade your server. However, configuring swap space can give you more flexibility and can help buy you time on a less powerful server.
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