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Which new feature allows a DBA to connect to an unresponsive database?
Emergency Monitoring
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In Emergency Monitoring, to what does the DBA connect?
Directly to the SGA, bypassing the SQL layer
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In Emergency Monitoring how does one connect to the database?
In diagnostic mode
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What is Emergency Monitoring similar to in 11g?
Memory Access Mode
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From where does Emergency Monitoring get its data?
- Historical data stored in ASH buffers
- This data is refreshed in real-time
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How long are ASH buffers designed to save performance data in the SGA?
60 mins, but not guaranteed
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What Oracle feature would help identify a blocking session when it's not possible to connect to the database?
Emergency Monitoring
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What does Real-Time ADDM allows?
Performing a root-cause analysis
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What is the difference between Real-Time ADDM and Normal ADDM?
Real-Time ADDM analyses only recent data, the last 10 mins
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From where does Real-Time ADDM get it's data?
ASH from the SGA
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Is Real-Time ADDM available in RAC?
Yes, can get data from the SGA of each instance
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In Real-Time ADDM how does one connect to the database?
Preferably in Normal mode, if not, diagnostic mode
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Which process controls real-time ADDM analysis?
MMON - Runs every three seconds
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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
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Where does MMON store Real-Time ADDM reports
In AWR
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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.
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Where can Real-Time ADDM reports be viewed?
- EMCC
- DBMS_ADDM.REAL_TIME_ADDM_REPORT function
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How is a Real-Time ADDM report generated at command line?
select dbms_addm.real_time_addm_report() from dual;
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Which views can be used to view Real-Time ADDM report information?
- DBA_HIST_REPORTS
- DBA_HIST_REPORTS_DETAILS.
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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
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In Emergency Monitoring and Real-Time ADDM, what is a Diagnostic Connection?
- One bypassing the SGA
- Latchless
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What is a Compare Period ADDM Report?
A way to compare two two AWR Reports, producing a single comparison report
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Which Oracle feature can help compare performance between a good period and a bad period?
Compare Period ADDM Report
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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
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What is SQL Commonality?
- The degree to which the SQL statements, the workloads, and the applications are similar between
- two periods of time
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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
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How are Compare Period ADDM Reports generated?
- EMCC
- DBMS_ADDM.COMPARE_xxxxxx function
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What can be compared in Compare Period ADDM Reports?
- COMPARE_INSTANCE
- COMPARE_DATABASES
- COMPARE_CAPTURE_REPLAY_REPORT
- COMPARE_REPLAY_REPLAY_REPORT
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What do Compare Period ADDM Reports rely on
AWR snapshots
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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.
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All which parameter will log all DDL changes?
enable_ddl_logging=true
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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
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What is required to use enable_ddl_logging?
License the Oracle Change Management Pack
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What can be used to format the DDL logging log.xml into more a readable format
The show log command in adrci
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If an error deemed not important enough for the alert log is generated, where does it go?
The Debug Log
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Where is the Debug log written?
$ADR_HOME/log/debug
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In what format is the Debug log?
Same as the alert log
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What is Oracle Network Compression?
- A way of increasing performance in a system constrained by bandwidth
- Requires Oracle Advanced Compression Option
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Where is Oracle Network Compression configured?
In sqlnet.ora
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What the the parameters for Oracle Network Compression?
- SQLNET.COMPRESSION (OFF(def)|ON)
- SQLNET.COMPRESSION_LEVELS (LOW(def)|HIGH)
- SQLNET.COMPRESSION_THRESHOLD 1024 bytes
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What does SQLNET.COMPRESSION_THRESHOLD do?
Defines the size of data before compression is applied
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What is SDU size?
- Session Data Unit
- Size of packets transmitted over the network.
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What is the recommended size of the SDU?
70 bytes bigger than the common message size
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How is the SDU size configured?
- In sqlnet.ora
- SQLNET.DEFAULT_SDU_SIZE
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What is the default and max size of the SDU?
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