IkIgai [reason to live]

What is your igikai?

Find out the purpose of living. ie. reason to see, listen, talk, think, do and LIVE.

Pl. Refer this Resources : 

Here are a few resources for learning more about ikigai:

• Book: Ikigai, The Japanese Secret to a Long and Happy Life by Hector Garcia and Francesc Miralles
• Video: Ted Talk, How to Ikigai, Tim Tamashiro
• Video: Ted Talk, Don’t Wait to Find Your Ikigai, Gangadharan Menon

ikiGAI : iki : life   Gai: worth

Verb : Action : To serve, create, delight, nourish, provide, teach,heal,connect, Build.

What is Moai: [Group of life long friends]

Social group supports social, financial, health or spiritual interests.

IN US, Blue zones devoted to help live longer, better lives by sharing the lessons of the longest-lived cultures.

Meet frequently for a commom purpose.

HARA HACHI BU: [eat 80%]

VOC - Voice of Customer Training Basics

VOC techniques

Customer is God, Customer comes first, Always Right, All about Customers,

VOC : Market Reseacrch Term that describes customer feedback

Voice of Customer used in Business : in-depth process to capture customers expectation, preferences,  dislikes.

Produces detailed set of customer wants and needs

Used at the start of new product, process or service design initiative

Focus groups, surveys, individual interviews, others etc.

Basics:

Customer ?

is a person in and organization i/p to o/p.

is a person order/work for the success of your employees.

Customers can be grouped in to segments.

Internal and external by demographics

internal : directly connect to the organization, stack holders, share holders or employees, creditors 

external - not directly connected to the organization.

Significance of internal customer: Critical Role player/ Service Producer

Significance of external customer: responsible for success /survival of an enterprise. refer your business, repeat orders.

Consumer segments customers by AGe: eg Washing m/c target the home makers, play station targets for younger gen,

Segmentation By profession, By location, By Gender, By Lang, By age, BY climate etc.

Language and Local Practices are part of Segmentation.

Kellogs eg. Corn Flakes in India. Failure. Comparing the practices of India and American.

Consumer in US, consume flakjes with cold milk allows flakes to crispy.

In India, Heat milk before consumption, flakes turn soggy before consumption. Add sugar to milk. Sweet Breakfast, which does not go well in India.

Construct a list of customers within each segment. All customers (or atleast their concerns) must be represented.

Customer is God. With out u/s the customers needs, organization can not exist.

Advantages of VOC Analytics:

+To steal market share of competitor

+To generate new product and service ideas.

+To refine marketing language and campaigns to reflects consumer language and perception

Here are a few general questions you can ask:

• Why aren't customers returning?
• How can we market our products more effectively?
• What other product categories are our customers looking for?
• Why is the average order volume (AOV) dropping month over month?

These types of questions can lead to even more specific questions that can help you reach the root of the issue.

Have VOC Strategy

Collect Data by surveys, interviews & Focus Groups, Live chat, email, fb Forms. Analyze and  draw conclusions.

Listen to your customers.

Make more customer centric: Vision and clarity, Strong Leadership, Complete alignment with top, middle and bottom teams of management, 

Customer satisfaction nd experience are pinnacles of a successful business.

Analysis depends upon the types of product, type of dat a we collect.

Quantitative analysis like avg, max, min.

Qualitative requires a complex approach to ensure properly synthesize and summarize data we collect.

.

JVM Garbage Collection GC#003 (How)

 GC is a marvel of Java.

How to get GC Log so that we know what iss is happening , what is the foot print of execution phase image:

Let us explore the switches available for GC collection statistics in JVM 

GC Logging Flags in Java 8 and Earlier

 -XX:+PrintGC

-XX:+PrintGCDetails

 -XX:+PrintGCDateStamps and -XX:+PrintGCTimeStamps

-Xloggc

eg : java -cp $CLASSPATH -Xloggc mypackage.MainClass

                 or

   java -cp $CLASSPATH -Xloggc:/tmp/gc.log mypackage.MainClass 

GC Logging Flags in Java 9 and Later

eg: 

java -cp $CLASSPATH -Xlog:gc*=debug:file=/tmp/gc.log mypackage.MainClass

java -cp $CLASSPATH -Xlog:gc*=debug:stdout -Xlog:gc*=debug:file=/tmp/gc.log mypackage.MainClass

Networ{k|th} - Tutorials

 Network Commands

1. ipconfig /all  will return  bio-data of your n/w 

C:\Users\rmcme>ipconfig  /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : LaptopDELL
   Primary Dns Suffix  . . . . . . . :
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No
   DNS Suffix Search List. . . . . . : cable.rcn.com
Unknown adapter Local Area Connection:
   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : TAP-Windows Adapter V9
   Physical Address. . . . . . . . . : 00-FF-86-58-B1-15
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
Wireless LAN adapter Local Area Connection* 1:
   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Microsoft Wi-Fi Direct Virtual Adapter
   Physical Address. . . . . . . . . : 7C-67-A2-80-DA-69
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
Wireless LAN adapter Local Area Connection* 2:
   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Microsoft Wi-Fi Direct Virtual Adapter #2
   Physical Address. . . . . . . . . : 7E-67-A2-80-DA-68
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
Wireless LAN adapter Wi-Fi:
   Connection-specific DNS Suffix  . : cable.rcn.com
   Description . . . . . . . . . . . : Intel(R) Dual Band Wireless-AC 3165
   Physical Address. . . . . . . . . : 7C-67-A2-80-DA-68
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   Link-local IPv6 Address . . . . . : fe80::7a8a:c454:b45:988b%16(Preferred)
   IPv4 Address. . . . . . . . . . . : 192.168.0.34(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : Thursday, April 13, 2023 2:37:54 PM
   Lease Expires . . . . . . . . . . : Friday, April 14, 2023 2:37:53 PM
   Default Gateway . . . . . . . . . : 192.168.0.1
   DHCP Server . . . . . . . . . . . : 192.168.0.1
   DHCPv6 IAID . . . . . . . . . . . : 159147938
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-28-A7-A0-21-7C-67-A2-80-DA-68
   DNS Servers . . . . . . . . . . . : 208.59.247.45
                                       208.59.247.46
   NetBIOS over Tcpip. . . . . . . . : Enabled
Ethernet adapter Bluetooth Network Connection:
   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Bluetooth Device (Personal Area Network)
   Physical Address. . . . . . . . . : 7C-67-A2-80-DA-6C
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
C:\Users\rmcme>

2.nslookup ipaddress

C:\Users\rmcme>nslookup ycrash.io

Server:  ns2.dns.rcn.net
Address:  208.59.247.45
Non-authoritative answer:
Name:    ycrash.io
Addresses:  52.8.222.182
          52.8.184.141

C:\Users\rmcme>nslookup 142.251.163.100

Server:  ns2.dns.rcn.net
Address:  208.59.247.45
Name:    wv-in-f100.1e100.net
Address:  142.251.163.100

 3. ping amazon.com

Pinging amazon.com [205.251.242.103] with 32 bytes of data:

Reply from 205.251.242.103: bytes=32 time=125ms TTL=236
Reply from 205.251.242.103: bytes=32 time=35ms TTL=236
Reply from 205.251.242.103: bytes=32 time=37ms TTL=236
Reply from 205.251.242.103: bytes=32 time=34ms TTL=236
Ping statistics for 205.251.242.103:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 34ms, Maximum = 125ms, Average = 57ms

4. tracert google.com

Tracing route to amazon.com [205.251.242.103]

over a maximum of 30 hops:

  1     8 ms    16 ms    21 ms  192.168.0.1

  2   171 ms    62 ms    46 ms  172.30.0.1

  3    38 ms    96 ms    48 ms  216.80.78.77

  4    12 ms    33 ms   215 ms  207.172.17.3

  5   133 ms    16 ms    33 ms  hge0-0-0-6.border1.eqnx.il.rcn.net [207.172.19.243]

  6    36 ms    37 ms    35 ms  99.83.94.240

  7     *        *        *     Request timed out.

  8     *        *        *     Request timed out.

  9     *        *        *     Request timed out.

 10    37 ms    33 ms    30 ms  150.222.212.43

 11     *        *        *     Request timed out.

 12     *        *        *     Request timed out.

 13     *        *        *     Request timed out.

 14     *        *        *     Request timed out.

 15     *......

5. netstat -a 

    

Active Connections

  Proto  Local Address          Foreign Address        State

  TCP    0.0.0.0:135            LaptopDELL:0           LISTENING

  TCP    0.0.0.0:445            LaptopDELL:0           LISTENING

  TCP    0.0.0.0:3648           LaptopDELL:0           LISTENING

  TCP    0.0.0.0:5040           LaptopDELL:0           LISTENING

  TCP    0.0.0.0:6646           LaptopDELL:0           LISTENING

  TCP    0.0.0.0:7070           LaptopDELL:0           LISTENING

  TCP    0.0.0.0:7680           LaptopDELL:0           LISTENING

  TCP    0.0.0.0:7779           LaptopDELL:0           LISTENING

  TCP    0.0.0.0:49664          LaptopDELL:0           LISTENING

  TCP    0.0.0.0:49665          LaptopDELL:0           LISTENING

  TCP    0.0.0.0:49666          LaptopDELL:0           LISTENING

  TCP    0.0.0.0:49667          LaptopDELL:0           LISTENING

  TCP    0.0.0.0:49668          LaptopDELL:0           LISTENING

  TCP    0.0.0.0:49670          LaptopDELL:0           LISTENING

  TCP    127.0.0.1:27015        LaptopDELL:0           LISTENING

  TCP    127.0.0.1:50051        LaptopDELL:0           LISTENING

  TCP    127.0.0.1:55500        LaptopDELL:0           LISTENING

  TCP    192.168.0.34:139       LaptopDELL:0           LISTENING

  TCP    192.168.0.34:55453     relay-e24ffb83:https   ESTABLISHED

  TCP    192.168.0.34:55467     52.159.126.152:https   ESTABLISHED

  TCP    192.168.0.34:55518     20.25.241.18:https     ESTABLISHED

  TCP    192.168.0.34:55616     ec2-54-175-191-204:https  ESTABLISHED

  TCP    192.168.0.34:55635     52.96.170.82:https     ESTABLISHED

  TCP    192.168.0.34:55647     104.26.3.186:https     ESTABLISHED

  TCP    192.168.0.34:55846     52.96.79.226:https     ESTABLISHED

  TCP    192.168.0.34:55855     gb-in-f188:5228        ESTABLISHED

  TCP    192.168.0.34:55856     bg-in-f188:5228        ESTABLISHED

  TCP    192.168.0.34:56650     a23-7-28-47:https      ESTABLISHED

  TCP    192.168.0.34:56950     132.145.172.253:https  ESTABLISHED

  TCP    192.168.0.34:56985     a23-193-200-115:https  CLOSE_WAIT

  TCP    192.168.0.34:56986     a23-193-200-115:https  CLOSE_WAIT

  TCP    192.168.0.34:56987     a23-193-200-115:https  CLOSE_WAIT

  TCP    192.168.0.34:56988     a23-193-200-115:https  CLOSE_WAIT

  TCP    192.168.0.34:56989     a23-193-200-115:https  CLOSE_WAIT

  TCP    192.168.0.34:56990     a23-193-200-115:https  CLOSE_WAIT

  TCP    192.168.0.34:57038     bi-in-f191:https       ESTABLISHED

  TCP    192.168.0.34:57081     wv-in-f91:https        ESTABLISHED

  TCP    192.168.0.34:57134     lga34s30-in-f3:https   ESTABLISHED

  TCP    192.168.0.34:57205     bl-in-f156:https       TIME_WAIT

  TCP    192.168.0.34:57221     bl-in-f95:https        TIME_WAIT

  TCP    192.168.0.34:57243     ord37s43-in-f6:https   CLOSE_WAIT

  TCP    192.168.0.34:57251     bg-in-f138:https       ESTABLISHED

  TCP    192.168.0.34:57284     ord38s28-in-f6:https   TIME_WAIT

  TCP    192.168.0.34:57285     bj-in-f156:https       TIME_WAIT

  TCP    192.168.0.34:57286     ord38s30-in-f2:https   TIME_WAIT

  TCP    192.168.0.34:57291     ww-in-f99:https        TIME_WAIT

  TCP    192.168.0.34:57296     ec2-54-175-191-203:https  TIME_WAIT

  TCP    192.168.0.34:57302     e2a:https              TIME_WAIT

  TCP    192.168.0.34:57310     bh-in-f94:https        ESTABLISHED

  TCP    192.168.0.34:57311     ww-in-f102:https       ESTABLISHED

  TCP    192.168.0.34:57312     bl-in-f139:https       ESTABLISHED

  TCP    192.168.0.34:57315     kix06s05-in-f3:https   ESTABLISHED

  TCP    192.168.0.34:57321     wv-in-f113:https       ESTABLISHED

  TCP    192.168.0.34:57322     wv-in-f113:https       TIME_WAIT

  TCP    192.168.0.34:57332     wv-in-f119:https       ESTABLISHED

  TCP    192.168.0.34:57333     47:https               ESTABLISHED

  TCP    192.168.0.34:57337     ord38s33-in-f10:https  ESTABLISHED

  TCP    192.168.0.34:57338     bg-in-f95:https        ESTABLISHED

  TCP    192.168.0.34:57339     ec2-3-17-93-252:https  ESTABLISHED

  TCP    192.168.0.34:57341     bl-in-f102:https       ESTABLISHED

  TCP    192.168.0.34:57343     lga25s71-in-f3:https   ESTABLISHED

  TCP    192.168.0.34:57345     ec2-54-175-191-203:https  ESTABLISHED

  TCP    192.168.0.34:57347     13.68.233.9:https      ESTABLISHED

  TCP    [::]:135               LaptopDELL:0           LISTENING

  TCP    [::]:445               LaptopDELL:0           LISTENING

  TCP    [::]:3648              LaptopDELL:0           LISTENING

  TCP    [::]:7680              LaptopDELL:0           LISTENING

  TCP    [::]:7779              LaptopDELL:0           LISTENING

  TCP    [::]:49664             LaptopDELL:0           LISTENING

  TCP    [::]:49665             LaptopDELL:0           LISTENING

  TCP    [::]:49666             LaptopDELL:0           LISTENING

  TCP    [::]:49667             LaptopDELL:0           LISTENING

  TCP    [::]:49668             LaptopDELL:0           LISTENING

  TCP    [::]:49670             LaptopDELL:0           LISTENING

  TCP    [::1]:49669            LaptopDELL:0           LISTENING

  UDP    0.0.0.0:123            *:*

  UDP    0.0.0.0:500            *:*

  UDP    0.0.0.0:4500           *:*

  UDP    0.0.0.0:5050           *:*

  UDP    0.0.0.0:5353           *:*

  UDP    0.0.0.0:5353           *:*

  UDP    0.0.0.0:5353           *:*

  UDP    0.0.0.0:5353           *:*

  UDP    0.0.0.0:5353           *:*

  UDP    0.0.0.0:5355           *:*

  UDP    0.0.0.0:6646           *:*

  UDP    0.0.0.0:50001          *:*

  UDP    127.0.0.1:1900         *:*

  UDP    127.0.0.1:49664        *:*

  UDP    127.0.0.1:60146        *:*

  UDP    127.0.0.1:64458        *:*

  UDP    127.0.0.1:64459        *:*

  UDP    192.168.0.34:137       *:*

  UDP    192.168.0.34:138       *:*

  UDP    192.168.0.34:1900      *:*

  UDP    192.168.0.34:60145     *:*

  UDP    [::]:123               *:*

  UDP    [::]:500               *:*

  UDP    [::]:4500              *:*

  UDP    [::]:5353              *:*

  UDP    [::]:5353              *:*

  UDP    [::]:5353              *:*

  UDP    [::]:5355              *:*

  UDP    [::1]:1900             *:*

  UDP    [::1]:60144            *:*

  UDP    [fe80::7a8a:c454:b45:988b%16]:1900  *:*

  UDP    [fe80::7a8a:c454:b45:988b%16]:60143  *:*

6. arp -a

Interface: 192.168.0.34 --- 0x10

  Internet Address      Physical Address      Type

  192.168.0.1           0c-cb-85-f9-ad-ad     dynamic

  192.168.0.11          ec-b5-fa-0e-03-39     dynamic

  192.168.0.22          dc-9a-7d-21-b3-4b     dynamic

  192.168.0.255         ff-ff-ff-ff-ff-ff     static

  224.0.0.22            01-00-5e-00-00-16     static

  224.0.0.251           01-00-5e-00-00-fb     static

  224.0.0.252           01-00-5e-00-00-fc     static

  239.255.102.18        01-00-5e-7f-66-12     static

  239.255.255.250       01-00-5e-7f-ff-fa     static

  255.255.255.255       ff-ff-ff-ff-ff-ff     static

7. C:\Users\rmcme>route print

===========================================================================

Interface List

 11...00 ff 86 58 b1 15 ......TAP-Windows Adapter V9

 12...7c 67 a2 80 da 69 ......Microsoft Wi-Fi Direct Virtual Adapter

  7...7e 67 a2 80 da 68 ......Microsoft Wi-Fi Direct Virtual Adapter #2

 16...7c 67 a2 80 da 68 ......Intel(R) Dual Band Wireless-AC 3165

 14...7c 67 a2 80 da 6c ......Bluetooth Device (Personal Area Network)

  1...........................Software Loopback Interface 1

===========================================================================

IPv4 Route Table

===========================================================================

Active Routes:

Network Destination        Netmask          Gateway       Interface  Metric

          0.0.0.0          0.0.0.0      192.168.0.1     192.168.0.34     55

        127.0.0.0        255.0.0.0         On-link         127.0.0.1    331

        127.0.0.1  255.255.255.255         On-link         127.0.0.1    331

  127.255.255.255  255.255.255.255         On-link         127.0.0.1    331

      192.168.0.0    255.255.255.0         On-link      192.168.0.34    311

     192.168.0.34  255.255.255.255         On-link      192.168.0.34    311

    192.168.0.255  255.255.255.255         On-link      192.168.0.34    311

        224.0.0.0        240.0.0.0         On-link         127.0.0.1    331

        224.0.0.0        240.0.0.0         On-link      192.168.0.34    311

  255.255.255.255  255.255.255.255         On-link         127.0.0.1    331

  255.255.255.255  255.255.255.255         On-link      192.168.0.34    311

===========================================================================

Persistent Routes:

  None

IPv6 Route Table

===========================================================================

Active Routes:

 If Metric Network Destination      Gateway

  1    331 ::1/128                  On-link

 16    311 fe80::/64                On-link

 16    311 fe80::7a8a:c454:b45:988b/128

                                    On-link

  1    331 ff00::/8                 On-link

 16    311 ff00::/8                 On-link

===========================================================================

Persistent Routes:

  None

C:\Users\rmcme>

8. C:\Users\rmcme>systeminfo

Host Name:                 LAPTOPDELL

OS Name:                   Microsoft Windows 10 Home

OS Version:                10.0.19044 N/A Build 19044

OS Manufacturer:           Microsoft Corporation

OS Configuration:          Standalone Workstation

OS Build Type:             Multiprocessor Free

Registered Owner:          rmcmeera@gmail.com

Registered Organization:   N/A

Product ID:                00325-96142-21539-AAOEM

Original Install Date:     9/23/2021, 12:24:43 PM

System Boot Time:          4/2/2023, 1:29:43 PM

System Manufacturer:       Dell Inc.

System Model:              Inspiron 13-7378

System Type:               x64-based PC

Processor(s):              1 Processor(s) Installed.

                           [01]: Intel64 Family 6 Model 142 Stepping 9 GenuineIntel ~2901 Mhz

BIOS Version:              Dell Inc. 1.27.0, 1/18/2019

Windows Directory:         C:\WINDOWS

System Directory:          C:\WINDOWS\system32

Boot Device:               \Device\HarddiskVolume1

System Locale:             en-us;English (United States)

Input Locale:              en-us;English (United States)

Time Zone:                 (UTC-06:00) Central Time (US & Canada)

Total Physical Memory:     12,158 MB

Available Physical Memory: 4,834 MB

Virtual Memory: Max Size:  20,862 MB

Virtual Memory: Available: 11,273 MB

Virtual Memory: In Use:    9,589 MB

Page File Location(s):     C:\pagefile.sys

Domain:                    WORKGROUP

Logon Server:              \\LAPTOPDELL

Hotfix(s):                 18 Hotfix(s) Installed.

                           [01]: KB5022502

                           [02]: KB4562830

                           [03]: KB5003791

                           [04]: KB5012170

                           [05]: KB5025221

                           [06]: KB5006753

                           [07]: KB5007273

                           [08]: KB5011352

                           [09]: KB5011651

                           [10]: KB5014032

                           [11]: KB5014671

                           [12]: KB5015895

                           [13]: KB5016705

                           [14]: KB5018506

                           [15]: KB5020372

                           [16]: KB5022924

                           [17]: KB5023794

                           [18]: KB5005699

Network Card(s):           3 NIC(s) Installed.

                           [01]: Intel(R) Dual Band Wireless-AC 3165

                                 Connection Name: Wi-Fi

                                 DHCP Enabled:    Yes

                                 DHCP Server:     192.168.0.1

                                 IP address(es)

                                 [01]: 192.168.0.34

                                 [02]: fe80::7a8a:c454:b45:988b

                           [02]: Bluetooth Device (Personal Area Network)

                                 Connection Name: Bluetooth Network Connection

                                 Status:          Media disconnected

                           [03]: TAP-Windows Adapter V9

                                 Connection Name: Local Area Connection

                                 Status:          Media disconnected

Hyper-V Requirements:      VM Monitor Mode Extensions: Yes

                           Virtualization Enabled In Firmware: Yes

                           Second Level Address Translation: Yes

                           Data Execution Prevention Available: Yes

9. pathping 127.0.0.1

Tracing route to LaptopDELL [127.0.0.1]

over a maximum of 30 hops:

  0  LaptopDELL [127.0.0.1]

  1  LaptopDELL [127.0.0.1]

Computing statistics for 25 seconds...

            Source to Here   This Node/Link

Hop  RTT    Lost/Sent = Pct  Lost/Sent = Pct  Address

  0                                           LaptopDELL [127.0.0.1]

                                0/ 100 =  0%   |

  1    0ms     0/ 100 =  0%     0/ 100 =  0%  LaptopDELL [127.0.0.1]

Trace complete.

pathping ycrash.io

Tracing route to ycrash.io [52.8.222.182]

over a maximum of 30 hops:

  0  LaptopDELL.cable.rcn.com [192.168.0.34]

  1  192.168.0.1

  2  172.30.0.1

  3  216.80.78.77

  4  207.172.17.1

  5  207.172.17.79

  6  lag-107.ear4.Chicago2.Level3.net [4.26.123.5]

  7     *        *     ae2.3608.ear7.Chicago2.level3.net [4.69.142.178]

  8  52.95.217.36

  9  15.230.18.69

 10  52.95.62.31

 11     *        *        *

Computing statistics for 250 seconds...............

Source to Here   This Node/Link

Hop  RTT    Lost/Sent = Pct  Lost/Sent = Pct  Address

  0                                           LaptopDELL.cable.rcn.com [192.168.0.34]

                                3/ 100 =  3%   |

  1   92ms     4/ 100 =  4%     1/ 100 =  1%  192.168.0.1

                                0/ 100 =  0%   |

  2   11ms    99/ 100 = 99%    96/ 100 = 96%  172.30.0.1

                                0/ 100 =  0%   |

  3   56ms     7/ 100 =  7%     4/ 100 =  4%  216.80.78.77

                                0/ 100 =  0%   |

  4  ---     100/ 100 =100%    97/ 100 = 97%  207.172.17.1

                                0/ 100 =  0%   |

  5   95ms     5/ 100 =  5%     2/ 100 =  2%  207.172.17.79

                                0/ 100 =  0%   |

  6  129ms     3/ 100 =  3%     0/ 100 =  0%  lag-107.ear4.Chicago2.Level3.net [4.26.123.5]

                                1/ 100 =  1%   |

  7  126ms     4/ 100 =  4%     0/ 100 =  0%  ae2.3608.ear7.Chicago2.level3.net [4.69.142.178]

                               96/ 100 = 96%   |

  8  ---     100/ 100 =100%     0/ 100 =  0%  52.95.217.36

                                0/ 100 =  0%   |

  9  ---     100/ 100 =100%     0/ 100 =  0%  15.230.18.69

                                0/ 100 =  0%   |

 10  ---     100/ 100 =100%     0/ 100 =  0%  52.95.62.31

Trace complete.

10. C:\Users\rmcme>hostname

LaptopDELL

11. C:\Users\rmcme>getmac

Physical Address    Transport Name

=================== ==========================================================

7C-67-A2-80-DA-68   \Device\Tcpip_{AA418031-63C2-4732-8243-7417259E49D6}

7C-67-A2-80-DA-6C   Media disconnected

00-FF-86-58-B1-15   Media disconnected

C:\Users\rmcme>

JVM - Garbage Collection GC #002

 Garbage Collection : GC#2

GC traverses the object  graph to find the dead objects.
Many types of GC collectors in Java. How to choose the right one.

Serial : Simplest, designed for small apps and on single thread.GC events are conducted serially in                      1 thread. Stop the world approach. So it is not used in real time.

Parellel : Multiple threads are used for minor gC in young generation. A single thread is used for                           Major GC. Most suitable for Multiple thread environment where a lot of work to be                               done, long pauses are accepted..(ie : running a batch job)
       It is the default since JDK 7

Concurrent Mark Sweep :

Concurrent low pause collector, multiple threads are used for minor garbage collection.

Major GC is multi threaded and runs concurrently alongside application. Use more CPUS.

If you can allocate ore CPU, the CMS GC is a preferre3d chice for better performance.

Garbage Firs (G1):

Replacement for CMS

Designed for multi-threaded apps that have large heap size available (>4 GB)

                 Does not have separate regions for young and old generations.

Partition the heap in to a set of equal size regions and use multiple[le threads to scan them.

After mark phase is over, G1 knows which regions contains the most garbage objects and performs GC on those regions first.

Experimental Garbage Collectors.

Epsilon : a -do- nothing (no-op) GC release as part of JDK 11.  Does not implement any memory                          reclamation mechanism. Not preferable. Once Heap is exhausted, the JVM shuts down

Shenandoah: Release as part of JDK 12. GC cycle works currently with application threads. Can                                 relocate objects concurrently. More CPU intensive.

ZGC : Release as part of JDK 11. Low latency, scalability and ease of use. Allows to application                        to continue running while it performs all garbage collection operations.

 

How to choose :

Factors : Most of the default setting will work.

Serial is fine for small data setup (>=100 MB) and or it will be run on a sigle processor with no-pause time requirements.

Parallel is preferable for peak performance for apps  and with no-pause time requirements or pauses for 1 sec or longer are acceptable.

CMS/G1 is preferable is response time is important than overall throughput and garbage collection pauses must be kept shorter than approximately 1 sec.

 

Advantages of GC :

Makes code simple, java memory efficient. Don't worry about mem management (C++                            should be manual not automatic mem management) .
Frees the heap mem to accommodate new objects.
Options for tuning the GC to improve its efficiency.

Best Practice:

It is possible to manually run the GC with System.gc() or Rintime.gc() methods.

If u don't have enough memory to run your application, you will experience slowdowns,                        hangs, long collection times, :stop the world" events, and eventually out of memory errors.                     You can take the help of monitoring tool like jstat or Java Flight recorder to see if the heap                       usage grows indefinitely, which might indicate a bug in your code.

If small, default settings will work.

Best approach to tuning JAVA garbage collection is settings flags on the JVM.

JVM - Garbage Collection - GC#001

 Garbage Collection - GC#1

Process of reclaiminh the runtime unused memory by destroying the un used objects

Methods like free() in C and deletete() in c++ are used to perform clean garbage.

In Java, GC is automatic during the life time of a program

At any point of RT, heap memory consistes of 2 types of objects:

Live : Being used and referenced

Dead : not used and not referenced currently.

How to derefernce objects:

By making a reference null { object o1 = null;}

By assigning a reference to another { object o1 = o2;}

By using an anonymous object { new Object;}

How GC Works:

       Many Versions of JVM. has its own implementation of GC .

       Any version of JVM can be used but should meet the std spec like :

: mark the unreachable objects

: Destroy them    

: Compacting the memory.

GC Roots: to identify the live and dead objects

Local vars and input paramas

        Active Threads

  Static Fields of the Loaded classes

JNI In(ref)ferences

It traverse the full object graph in mem and marks live objects(visited). ALl not reacheble(not visited) by grtaph are identified as dead objects.

Sweep Phase and compact phase ( Fragmented mem blocks are made as contiguos blocks)

Generational GC strategy:

Marking will take a longer GC Time. All objects are mostly short lived.

Heap : (eden, S1, S2)

        Young Generation : Newly 

-Eden Space : all new objects start here, and initial mem is allocated to them

-Survivor Spaces : (S to S)  - Objects are moved here from Eden after surviving one garbage collection cycle.

        When eden space if filled , aminor GC is performed and all the survivir objects are moved to one of the survivor spaces.

Minor GC checks also the survivor space. All the dead objects are reoved when Minir GC is performed.

Second time Minor GC, is used Eden and Survivor space. At any point of time Survivor space is empty.

        Old Generation : Long lived objects are eventually moved from the Young generation to the Old Generation.

This is also known as Tenured generation and conatins objects that have maintained in  the survivor spaces for a long time.

When objects are garbage collected here, it is called as majot garbage collection event.

Permenant Generation :

Metat data such as classes and methods are stored in Perm Genearation

Classes thar are no longer in use may be GC from the permenant generation.

Now Metaspace memory soppace replaced the permenant generation. Heap is now automatically resized. Avoids the the pbm of apps going out of memory due to the limited size of 

PermGen space of heap.

Classes that are no longer used is automatically cleaned when the metaspace searches its maximum size.

JVM - Basics #01

JVM

Java Virtual Machine implements Write once Run Anywhere approach 

Supports many Scala, Kotlin in addition to Java

-> VM -> OS -> Application 

Virtual M/C : H/W-> Hypervisor-> -> VM -> OS -> App.. 

-> VM -> OS -> App..

Java - Compiler - SC (Java) - > Byte code (class) -> 

       

JVM : 

Class Loader : Prepares the java classes and loads them into main memory.

Run Time Mem/ Data Area: Holds the the rT vars and Data

Execution Engine : Executes the code

Class Loader : 

Loading :  Boot strap Loader, Extension Class Loader, Application Class Loader

        Bin representation :

         Boot Strap Loader . Root Class Loader .. 

Super class of Extension loads the std java packages like java.lang, java.net, java.util, java.io                 etc.

The above are available in rt.jar file

         Extension Class Loader : Sub class of Bootstrap and the super class of thge Application class                                                            Loader.

Loads the files present in $JAVA_HOME/jre/lib/ext directory

Application Class Loader : subclass extensions loader, Loads the files present on the class                                                                  path

By Default, the class path is set to the current directory of th application.

Linking :  

Verification : Verify, Prepare and Resolve : check the structureal correctness of the .class file                                        by checking it against a set of constraint rules . Check for Verify                                                             Exception..

Preperation  : JVM allocates memory for stat fields of a class or interface. Initializes them                                          with default values.

Resolution   : Symbolic reference are substituted with direct references present in RT constant                                        pool.

         Initialization : 

Clinit .

                        Assigning values, constructor call, stat block exec, 
final stage of class loading. Also check for concurrency issues.
Handle thread safety issues for secured process.

Run Time Data Area:

Method Area : 

Class level data as RT Constant Pool, field and code for methods. Memory is insufficent for the startup, JVM throws outofMemoryError

Memory for class instances  and arrays is allocated.

Heap Area   :

All the objects and their corresponding instance varaiables and arrays are stored here. Created on startup. Only one heap Area/JVM

Stack Area  :

Local varsiables and temp results are stored here.
For every method call,  one entry is made into stack frame:
 Further divided in to local vars, operand stack, frame data    

PC Register : Program Counter Register. JVM supports multiple threads. Each thread has its own                                 PCR, to hold the address of currently executing JVM Instruction.

      Once executed, PCR is updated

Native Method Stack : JVM supports native methods. ( written in c/C++)

 

Execution Engine :

Byte code is loaded then interpreter 

       Reads BC line by line.
       JIT compiler : When EE finds the repeated code, it uses JIT-C, tot compile the en tire BC and                                        change it to native code.
JITC Consists of 3 components : Intermediate code Generator, Code Optimizer, Target Code                                                                      Generator.

Garbage Collector:

GC collects and removes un referenced objects.
Involves 2 phases : Mark and Sweep. Done automaticall by GC.
3 types of JC in KJVM, Serial, Parellel(through put)  and G1 (for large heap sizes > 4 GB)

  Java Native Interface 

Supports execution of native code via JNI (c, C++ or ASM files).

Better Teacher

3 Steps

Focus on Learning of students rather than teaching 

1. One rule is that people learn faster and better with varied repetition. Children who practice the piano twice a day are almost always better piano players than children who practice once a week. The same is true of speaking a foreign language, solving quadratic equations, and writing persuasive essays.

1. A second rule is that people learn faster and better when they receive frequent feedback on their performance. (A corollary to this rule is that prompt feedback is more effective than delayed feedback.)

1. A third rule is that incentives can play a crucial role in the classroom

Teachers can quiz students weekly and reveal the correct answers immediately. In this way, students receive prompt and frequent feedback. They also have an incentive to complete assigned readings and pay attention in class.

Finally, teachers can take a page from video-gaming companies. Video gaming is a learned skill, and many gamers perform at a very high level. The makers of popular video games like Angry Birds and Super Mario exploit basic principles of learning. Players receive instantaneous feedback on their performance. They also gain expertise through repetition with variation. And leveling up is rewarding!

Key:

• Teachers should think less about how to teach and more about how students learn.
• Studies have identified potent enablers of learning such as varied repetition, prompt feedback, and mental elaboration.
• Teachers can put these principles to work when they build courses, assignments, and tests

From Source