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Sunday, October 28, 2018
A Data Scientist is a person employed to analyse and interpret complex digital data, such as the usage statistics of a website, especially in order to assist a business in its decision-making.
A Data Scientist is a person who possesses most of the above mentioned Math + Technology + Business skill sets and extracts valuable information from the data for business".
A Data Scientist is a person who possesses most of the above mentioned Math + Technology + Business skill sets and extracts valuable information from the data for business".
Tuesday, October 23, 2018
Data Science is perfect amalgamation of programming, analytical, and business skills that allows extracting meaningful insights from raw and unstructured data.
Data Science is a study which deals with identification, representation and extraction of meaningful information from data sources to be used for business purposes.
With enormous amount of facts generating each minute, the requirement to extract the useful insights is a must for the businesses to stand out from the crowd. DBA setup the database and data storage in order to facilitate the process of data mining, data munging and other processes. Every other organization is running behind profits, but the companies that formulate efficient strategies based on fresh and useful insights always win the game in the long-run.
Thursday, August 16, 2018
Issue :
We often come across a scenario in which MRP0 process stop applying logs and the status of it will be WAIT_FOR_LOG.
Workaround :
Check LNS on Primary Database: Writing
SQL> select inst_id, process, status, thread#, sequence#, block#, blocks from gv$managed_standby where process in ('RFS','LNS','MRP0');
INST_ID PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
---------- --------- ------------ ---------- ---------- ---------- ----------
2 LNS WRITING 2 74 17873 1
1 LNS WRITING 1 79 24255 1
LNS Process :
In Data Guard, LNS process performs actual network I/O and waits for each network I/O to complete.
The NET_TIMEOUT attribute is used only when the LGWR process transmits redo data using a LGWR Network Server(LNS) process.
Check MRP0 on Standby Database: WAIT_FOR_LOG
SQL> select inst_id, process, status, thread#, sequence#, block#, blocks from gv$managed_standby where process in ('RFS','LNS','MRP0');
INST_ID PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 1 79 25361 1
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 MRP0 WAIT_FOR_LOG 2 74 0 0
Check Broker Status
Check the apply lag by the broker.
Database - standb
Role: PHYSICAL STANDBY
Intended State: APPLY-ON
Transport Lag: 0 seconds
Apply Lag: 2 hour(s) 55 minutes 47 seconds
Real Time Query: OFF
Instance(s):
standb1
standb2 (apply instance)
Database Status:
SUCCESS
Apply Lag: We can clearly see the difference of 2 hour(s) 55 minutes 47 seconds
Re-enable Standby Database
DGMGRL> enable database standb;
Enabled.
Now check the status again.
SQL> select inst_id, process, status, thread#, sequence#, block#, blocks from gv$managed_standby where process in ('RFS','LNS','MRP0');
INST_ID PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
---------- --------- ------------ ---------- ---------- ---------- ----------
1 RFS RECEIVING 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 1 80 58 1
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 MRP0 APPLYING_LOG 1 79 24581 25582
Now it’s back to normal. APPLYING_LOG is the normal status for real-time applying service.
We often come across a scenario in which MRP0 process stop applying logs and the status of it will be WAIT_FOR_LOG.
Workaround :
Check LNS on Primary Database: Writing
SQL> select inst_id, process, status, thread#, sequence#, block#, blocks from gv$managed_standby where process in ('RFS','LNS','MRP0');
INST_ID PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
---------- --------- ------------ ---------- ---------- ---------- ----------
2 LNS WRITING 2 74 17873 1
1 LNS WRITING 1 79 24255 1
LNS Process :
In Data Guard, LNS process performs actual network I/O and waits for each network I/O to complete.
The NET_TIMEOUT attribute is used only when the LGWR process transmits redo data using a LGWR Network Server(LNS) process.
Check MRP0 on Standby Database: WAIT_FOR_LOG
SQL> select inst_id, process, status, thread#, sequence#, block#, blocks from gv$managed_standby where process in ('RFS','LNS','MRP0');
INST_ID PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 1 79 25361 1
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 MRP0 WAIT_FOR_LOG 2 74 0 0
Check Broker Status
Check the apply lag by the broker.
Database - standb
Role: PHYSICAL STANDBY
Intended State: APPLY-ON
Transport Lag: 0 seconds
Apply Lag: 2 hour(s) 55 minutes 47 seconds
Real Time Query: OFF
Instance(s):
standb1
standb2 (apply instance)
Database Status:
SUCCESS
Apply Lag: We can clearly see the difference of 2 hour(s) 55 minutes 47 seconds
Re-enable Standby Database
DGMGRL> enable database standb;
Enabled.
Now check the status again.
SQL> select inst_id, process, status, thread#, sequence#, block#, blocks from gv$managed_standby where process in ('RFS','LNS','MRP0');
INST_ID PROCESS STATUS THREAD# SEQUENCE# BLOCK# BLOCKS
---------- --------- ------------ ---------- ---------- ---------- ----------
1 RFS RECEIVING 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 RFS IDLE 1 80 58 1
2 RFS IDLE 0 0 0 0
2 RFS IDLE 0 0 0 0
2 MRP0 APPLYING_LOG 1 79 24581 25582
Now it’s back to normal. APPLYING_LOG is the normal status for real-time applying service.
Sunday, August 12, 2018
Error :
Workaround :
This is mainly due to CD/DVD drive is locked by virtual machine.
We simply need to unmount the CD/DVD.
From Terminal :
Workaround :
This is mainly due to CD/DVD drive is locked by virtual machine.
We simply need to unmount the CD/DVD.
From Terminal :
Monday, August 6, 2018
# cd /media/vmware
# cp VMwaretools.9.tar.gz /tmp/
# cd /tmp/
# tar -xvf VMwaretools.9.tar.gz
# ls
# cd VMware-tool-distrib/
# ./VMware-install.pl
# cp VMwaretools.9.tar.gz /tmp/
# cd /tmp/
# tar -xvf VMwaretools.9.tar.gz
# ls
# cd VMware-tool-distrib/
# ./VMware-install.pl
Saturday, August 4, 2018
Note : If we want the " Desktop " Version / Graphical Version we can select here.
Tuesday, July 24, 2018
With Oracle 18c , the database software is in image file for download and installation.
RPM - Based Oracle Database Installation :
By using rpm-ivh command , an RPM based database installation performs pre - installation validations, ownshership
to users and groups, maintains the oracle inventory.
Read-Only Oracle Home :
If we chose a read only oracle home , then the database tools and process write under the ORACLE_BASE path instead
of under the oracle home directory.
Local Switch Home Command for Patching Databases
Oracle came up with new built-in tool , " rhpctl " that enables you to switch from current oracle database home to a patched
oracle database home.
Friday, June 29, 2018
SQL> alter table Details add (mobile varchar2(15));
*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified
Workaround :
1 . In Oracle 11g you can set ddl_lock_timeout i.e. allow DDL to wait
for the object to become available, simply specify how long you would like it to wait:
SQL> alter session set ddl_lock_timeout = 500;
Session altered.
SQL> alter table Details add (mobile varchar2(15));
Table altered.
2. We can mark your table as read-only to prevent DML:
SQL> alter table emp read only;
Session altered.
SQL> alter table Details add (mobile varchar2(15));
Table altered.
3. This workaround is not preferred on production database , can you use according to the criticality of the problem.
Identify the session which is locking the object
SQL> select a.sid, a.serial#
from v$session a, v$locked_object b, dba_objects c
where b.object_id = c.object_id
and a.sid = b.session_id
and OBJECT_NAME='Details';
kill that session using
SQL> alter system kill session 'sid,serial#';
*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified
Workaround :
1 . In Oracle 11g you can set ddl_lock_timeout i.e. allow DDL to wait
for the object to become available, simply specify how long you would like it to wait:
SQL> alter session set ddl_lock_timeout = 500;
Session altered.
SQL> alter table Details add (mobile varchar2(15));
Table altered.
2. We can mark your table as read-only to prevent DML:
SQL> alter table emp read only;
Session altered.
SQL> alter table Details add (mobile varchar2(15));
Table altered.
3. This workaround is not preferred on production database , can you use according to the criticality of the problem.
Identify the session which is locking the object
SQL> select a.sid, a.serial#
from v$session a, v$locked_object b, dba_objects c
where b.object_id = c.object_id
and a.sid = b.session_id
and OBJECT_NAME='Details';
kill that session using
SQL> alter system kill session 'sid,serial#';
Monday, June 25, 2018
[oracle@exdprd]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Jun 26 07:59:43 2018
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-09817: Write to audit file failed.
Linux-x86_64 Error: 28: No space left on device
Additional information: 12
ORA-01075: you are currently logged on
Workaround :
1. Check the free space of mount point /u01
[oracle@exdprd]$ df -h
2. Remove old and unwanted trace and audit files.
3 . Check the space now on mount pount /u01
4. Now we will be able to login successfully.
SQL*Plus: Release 11.2.0.4.0 Production on Tue Jun 26 07:59:43 2018
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-09817: Write to audit file failed.
Linux-x86_64 Error: 28: No space left on device
Additional information: 12
ORA-01075: you are currently logged on
Workaround :
1. Check the free space of mount point /u01
[oracle@exdprd]$ df -h
2. Remove old and unwanted trace and audit files.
3 . Check the space now on mount pount /u01
4. Now we will be able to login successfully.
Sunday, June 24, 2018
1 B (Byte) = 8 Bits.
1 KB (Kilo Byte) = 1024 B or 103 (Bytes).
1 MB (Mega Byte) = 1024 KB or 106 (Kilo Bytes).
1 GB (Giga Byte) = 1024 MB or 109 (Mega Bytes).
1 TB (Tera Byte) = 1024 GB or 1012 (Giga Bytes).
1 PB (Peta Byte) = 1024 TB or 1015 (Tera Bytes).
1 EB (Exa Byte) = 1024 PB or 1018 (Peta Bytes).
1 ZB (Zetta Byte) = 1024 EB or 1021 (Exa Bytes).
1 YB (Yotta Byte) = 1024 ZB or 1024 (Zetta Bytes).
1 (Bronto Byte) = 1024 YB or 1027 (Yotta Bytes).
1 (Geop Byte) = 1024 ZB or 1030 (Bronto Bytes).
1 KB (Kilo Byte) = 1024 B or 103 (Bytes).
1 MB (Mega Byte) = 1024 KB or 106 (Kilo Bytes).
1 GB (Giga Byte) = 1024 MB or 109 (Mega Bytes).
1 TB (Tera Byte) = 1024 GB or 1012 (Giga Bytes).
1 PB (Peta Byte) = 1024 TB or 1015 (Tera Bytes).
1 EB (Exa Byte) = 1024 PB or 1018 (Peta Bytes).
1 ZB (Zetta Byte) = 1024 EB or 1021 (Exa Bytes).
1 YB (Yotta Byte) = 1024 ZB or 1024 (Zetta Bytes).
1 (Bronto Byte) = 1024 YB or 1027 (Yotta Bytes).
1 (Geop Byte) = 1024 ZB or 1030 (Bronto Bytes).
Monday, January 15, 2018
Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.
The protocol is usually described in terms of a client-server model, but can as easily be used in peer-to-peer relationships where both peers consider the other to be a potential time source.
Clock synchronization :
A typical NTP client will regularly poll three or more servers on diverse networks. To synchronize its clock, the client must compute their time offset and round-trip delay.
Round Trip Delay :
d=(T4-T1)-(T2-T3)
Time Offset :
t=(T2-T1)+(T3-T4)/2
The protocol is usually described in terms of a client-server model, but can as easily be used in peer-to-peer relationships where both peers consider the other to be a potential time source.
Clock synchronization :
A typical NTP client will regularly poll three or more servers on diverse networks. To synchronize its clock, the client must compute their time offset and round-trip delay.
Round Trip Delay :
d=(T4-T1)-(T2-T3)
Time Offset :
t=(T2-T1)+(T3-T4)/2
