OOW: Day 3

A successful 11g installation – Plamen Zyumbyulev & Phil Newlan

First part of the presentation is from Plamen
trying to get to a dynamically configurable infrastracture moving to a service approach (oracle services)

effective automatic workload management with NO single point of failure. need centralised monitoring and management.

running linux x86-64 with blades, though he said privately that he was less than happy with them. Disadvantages include not low cost, limited I/O and limited flexibility.

Consolidation project moving many business systems into a smaller number of databases.

For DR Can actually just force logging on certain tablespaces

datafiles can have different redundancy within the same diskgroup

using workload management where sessions are assigned to consumer groups and only allowed certain % of resources.

with different services on separate nodes, dynamic resource re-mastering is useful to ensure the blocks are owned by the instances that are hosting the services rather than being spread around the whole cluster.

Note Mtel went live with a beta version of 11g though not mission critical stuff!

List of improvements in 11g:

Parallel Query integration with services so the query stays local to the instances upon which the service has been defined as active.

improvements to ASM, preferred read for stretched clusters.

Enterprise manager screen showing which failure group the instance is reading from. Obviously you must be using ASM mirroring to take advantage of this. Must have 11gR1 ASM and 11gR1 RDBMS

ASM Fast Disk Resync

loss of disk within a diskgroup will not cause an immediate rebalance. ASM keeps track of blocks that have changed when disk is back it syncs the changes. Again need to have implemented ASM mirroring. Only useful for temporary disk loss, not for swapping a disk out.

ADDM is now RAC aware in 11gR1. will identify the most globally significant performance problems with the entire RAC cluster rather than on an instance basis.

runtime connection pooling is integrated with RAC load balancing advisory so a new connection is given based on the load of the various instances routing to the instance that will (hopefully)  best response time.

Question regarding whether you can run with mismatched clusterware, ASM, RDBMS versions. yes you can but clusterware must be at the highest version. i,.e. 10g RDBMS with 11g clusterware.

REAL confusion over what happens when a disk in a failure group fails and how much space is required to rebalance.

Performance Fundamentals for oracle Database 10g & 11g – Graham Wood, & John Beresniewicz

This was such a popular session, that this is second running of it. Real title is DB Time performance tuning: Theory and Practice.

They are being a little sarcastic regarding enterprise manager.

Time

History of tuning methods comparing methods. Graham Wood has been using Oracle since Version 2.

DB Time is the total time in database calls by foreground sessions, includes cpu time, I/O time and non-idle wait time

DB Time <> response time

Database time is total time spent by user processes either actively working or actively waiting in a database call.

Response time for the end user is not just the time spent doing work in the db.

Active session is a session currently spending time in a database call

DB Time = Sum of DB Time over all sessions

Avg Active sessions = Total DB Time / Wall Clock (Elapsed) Time

Increasing load is either more sessions active

OR

same number sessions performing operations that take longer

DB Time increases when performance decreases

If host is CPU bound, foreground processes accumulate active run-queue time basically when a process is in the run-queue it may still be recording active DB Time as the session has not been able to signal that the wait is finished – as it’s waiting to get back on the CPU to record the fact.

This can manifest itself as though there is increased I/O wait time – when the real problem is waiting to get on CPU.

Techniques

where to fine DB Time

V$SYS_TIME_MODEL, V$SESS_TIME_MODEL

STAT_NAME = ‘DB time’

V$SYSMETRIC_HISTORY

“Database Time per Second” “CPU Usage Per Sec

V$SQL

ELASPED_TIME = DB Time within this view

V$ACTIVE_SESSION_HISTORY

All active sessions captured every second this view in memory has a 1 sec sampling, while DBA_HIST_ACTIVE_SESS_HISTORY

11g enhancement shows which row source is running within an SQL statement in.2 each sample

Tools

They completely overran and skipped this section and took no questions.

Changes, Changes, Changes – Tom Kyte

This is my first Tom Kyte session of Openworld.  Qutie a bit of the crowd claim to have been a DBA for 15 years.

Tom thinks that 11g is all about safely introducing change into the database.

increasing level off online changes as you through oracle versions

online parameter changes
online major memory changes
online schema evolution
online index creates
rolling upgrades – still to actually see that
online disk reconfiguration

Tom’s giving a review of standby databases.

Real Application Testing helps with testing changes.

Flashback technology helps recover from human error, various options flashback query, tables, database.

tom previewing package versions – this was meant to be in 11gR1 but did not make the cut. This will give online application upgrades.

In truth this was a bit of an anti-climax after the hype of the Exadata announcement.

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