Oracle 12c Upgrade: 15 – Emergency Monitoring, Real-Time ADDM
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. What would you like to do?
Which new feature allows a DBA to connect to an unresponsive database?
In Emergency Monitoring, to what does the DBA connect?
Directly to the SGA, bypassing the SQL layer
In Emergency Monitoring how does one connect to the database?
In diagnostic mode
What is Emergency Monitoring similar to in 11g?
Memory Access Mode
From where does Emergency Monitoring get its data?
- Historical data stored in ASH buffers
- This data is refreshed in real-time
How long are ASH buffers designed to save performance data in the SGA?
60 mins, but not guaranteed
What Oracle feature would help identify a blocking session when it's not possible to connect to the database?
What does Real-Time ADDM allows?
Performing a root-cause analysis
What is the difference between Real-Time ADDM and Normal ADDM?
Real-Time ADDM analyses only recent data, the last 10 mins
From where does Real-Time ADDM get it's data?
ASH from the SGA
Is Real-Time ADDM available in RAC?
Yes, can get data from the SGA of each instance
In Real-Time ADDM how does one connect to the database?
Preferably in Normal mode, if not, diagnostic mode
Which process controls real-time ADDM analysis?
MMON - Runs every three seconds
What will trigger a real-time ADDM analysis?
- If MMON spots
- High CPU load > 3xCPU Cores
- I/O - Reads on a single block impacting Active Sessions
- CPU Bound - Active sessions greater than 10% of total load. CPU > 50%
- Hung session - Hung sessions > 50% of total number of sessions
Where does MMON store Real-Time ADDM reports
What stops too many real-time ADDM analysis triggering?
- New reports will not be generated if a report was produced in the last 5 mins
- An automatic trigger for an impact must have an impact >100% than the previous report with the same triggering issue within the last 45 minutes.
Where can Real-Time ADDM reports be viewed?
- DBMS_ADDM.REAL_TIME_ADDM_REPORT function
How is a Real-Time ADDM report generated at command line?
select dbms_addm.real_time_addm_report() from dual;
Which views can be used to view Real-Time ADDM report information?
How are Emergency Monitoring and Real-Time ADDM used together?
- First use Emergency Monitoring for blocking session or very obvious things
- If nothing found, Real-Time ADDM can help get the the root cause by offering recommendations
In Emergency Monitoring and Real-Time ADDM, what is a Diagnostic Connection?
- One bypassing the SGA
What is a Compare Period ADDM Report?
A way to compare two two AWR Reports, producing a single comparison report
Which Oracle feature can help compare performance between a good period and a bad period?
Compare Period ADDM Report
What's the difference between AWR Compare Periods Report and Compare Period ADDM Report?
- AWR Compare Periods Report, which tells you what exactly is the difference in performance
- Compare Period ADDM Report tells you what you can attribute the changes to
What is SQL Commonality?
- The degree to which the SQL statements, the workloads, and the applications are similar between
- two periods of time
How does is SQL Commonality relate to Compare Period ADDM Reports?
- If the SQL Commonality < 80%, the report findings may not be too accurate/significant
- SQL Commonality is given at the beginning of a Compare Period ADDM Report
How are Compare Period ADDM Reports generated?
- DBMS_ADDM.COMPARE_xxxxxx function
What can be compared in Compare Period ADDM Reports?
What do Compare Period ADDM Reports rely on
Describe a Compare Period Report
- Overview - SQL Commonality
- Configuration - Difference in parameters
- Findings - Findings obv.
- Resources - Division of database time over the two periods
- CPU Memory, I/O and RAC interconnect.
All which parameter will log all DDL changes?
When enable_ddl_logging=true, where is the data logged?
- In 11g Alert Log
- In 12c to an exclusive log.xml in $ADR_HOME/home/ddl
What is required to use enable_ddl_logging?
License the Oracle Change Management Pack
What can be used to format the DDL logging log.xml into more a readable format
The show log command in adrci
If an error deemed not important enough for the alert log is generated, where does it go?
The Debug Log
Where is the Debug log written?
In what format is the Debug log?
Same as the alert log
What is Oracle Network Compression?
- A way of increasing performance in a system constrained by bandwidth
- Requires Oracle Advanced Compression Option
Where is Oracle Network Compression configured?
What the the parameters for Oracle Network Compression?
- SQLNET.COMPRESSION (OFF(def)|ON)
- SQLNET.COMPRESSION_LEVELS (LOW(def)|HIGH)
- SQLNET.COMPRESSION_THRESHOLD 1024 bytes
What does SQLNET.COMPRESSION_THRESHOLD do?
Defines the size of data before compression is applied
What is SDU size?
- Session Data Unit
- Size of packets transmitted over the network.
What is the recommended size of the SDU?
70 bytes bigger than the common message size
How is the SDU size configured?
- In sqlnet.ora
What is the default and max size of the SDU?
What would you like to do?
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