1. Chapter 20 Other Memory Management Topics

2. Overview Memory management in Oracle Result Cache
Oracle 10G: ASMM (Dynamic SGA)
Oracle 11G: AMM (Dynamic SGA & PGA)
Result Cache
Optimization of other memory areas
Shared Pool
Large Pool
Redo Buffer

3. Optimizing Overall Memory
AMM (Automatic Memory Management)
Oracle 11G feature
Let’s Oracle decide how to allocate between pools
Includes between SGA components and PGA
ASMM (Automatic Shared Memory Management)
Oracle 10g feature
Let’s Oracle decide how to allocate for SGA only
PGA still separate entity managed on it’s own

4. IO Wait Times / Memory Optimization
Memory optimization helps reduce IO
Categories of Oracle IO include:
Buffered datafile IO
Temporary segment IO waits
Direct path reads
System IO
See “Active Sessions Waiting” chart in OEM

5. Using Advisories For PGA In Oracle 11g In Oracle 10g
Look at V$PGA_TARGET_ADVICE
Includes elapsed times
Compare directly with V$DB_CACHE_ADVICE
In Oracle 10g
Need to calculate elapsed times outside of V$PGA_TARGET_ADVICE
Determine average time and block counts
Use averages to convert byte counts
Combine times with buffer cache advisory

6. AMM Enable by setting parameters Optionally set (minimum sizes for)
MEMORY_MAX_TARGET
MEMORY_TARGET
Optionally set (minimum sizes for)
SGA_TARGET
PGA_AGGREGATE_TARGET
Individual pool parameters, such as LARGE_POOL
Can also configure in OEM
Go to Advisor Central
Then to Memory Advisors

7. AMM (cont.) Monitoring Memory Allocations Views show useful statistics
Can monitor using several dynamic views
V$MEMORY_DYNAMIC_COMPONENTS
V$MEMORY_RESIZE_OPS
V$MEMORY_TARGET_ADVICE
Views show useful statistics
Current memory allocations
Minimum and maximum sizes
Details on each resize operation
Affect on performance for potential resize operations

8. AMM Issues & Considerations
Set minimum sizes for memory components
Helps avoid memory “thrashing”
Helps avoid “memory starvation”
Not all memory components are part of AMM
Nondefault buffer pools
AMM incompatible with “Linux HugePages”
Cannot lock SGA when using AMM (LOCK_SGA)

9. Result Set Cache Entire result sets stored in shared memory
Can help avoid
Parse time
Logical reads
Physical reads
Cache contention (e.g. latches)
Effective only in certain scenarios
Read only or nearly read only data
Small result sets
Needs to be used sparingly to avoid result cache latch contention
Expensive queries that meet above criteria
Can store PL/SQL Functions in cache in certain situations

10. Configuring the Result Cache
Set with parameters
RESULT_CACHE_MODE={OFF|MANUAL|FORCE}
RESULE_CACHE_MAX_SIZE (size of cache)
RESULT_CACHE_MAX_RESULT (maximum size of one result)
Monitor with V$RESULT_CACHE_STATISTICS
Monitor contention by looking for “latch free” waits
Use with caution:
RESULT_CACHE_MODE=FORCE
The RESULT_CACHE table property

11. Other Memory Optimizations
Sizing the Shared Pool
Moderately sized pool generally sufficient
See V$SHARED_POOL_ADVICE for help
Using bind variables important for efficiency
If not used, size increases usually not helpful
Review setting of CURSOR_SHARING parameter
Large Pool Sizing
Optional SGA component
Reduces shared pool fragmentation
Used for shared server configuraton
Used for parallel processes
Redo Log Buffer is generally small and self sufficient
Locking the SGA in memory helpful in certain scenarios