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The MEMORY_MAX_TARGET parameter is added to 11g, which is as refreshing as the first appearance of SGA_MAX_SIZE parameter in 10g. Memory_max_target is to set how much memory space Oracle can take up in OS, and one is how much memory space Oracle SGA area can take up. There is no doubt that 11gOracle is a step further towards automatic memory management.

The 10g sga_max_size allocates the Shared Pool Size,database buffer cache,large pool,javapool,redo log buffer size dynamically, only reallocating the memory blocks of the SGA according to the health of the Oracle. PGA needs to be set separately in 10g.

The 11gMEMORY_MAX_TARGET parameter contains two parts of memory, one System globalarea (SGA) and the other system globalarea (PGA). It is clear that PGA and SGA have been dynamically managed together in 11g.

Let's take a look at the impact of Memory_target settings and no settings on SGA/PGA in 11g:

A: if Memory_target is set to a non-zero value (there are four cases to allocate the size of SGA and PGA)

1) sga_target and pga_aggregate_target have been set the size if the parameters sga_target and pga_aggregate_target have been set in Oracle, these two parameters will be assigned to the minimum value as their target value.

Memory_Target=SGA_TARGET+PGA_AGGREGATE_TARGET, the same size as memory_max_size.

2) sga_target sets the size. If pga_aggregate_target does not set the size, then pga_aggregate_target initialization value = memory_target-sga_target

3) sga_target does not set the size, pga_aggregate_target sets the size, then the sga_target initialization value = memory_target-pga_aggregate_target

4) neither sga_target nor pga_aggregate_target set the size Oracle 11g. If neither sga_target nor pga_aggregate_target is set in size, Oracle will have no minimum and default values for these two values. Oracle allocates sizes based on the health of the database. However, when the database is started, there is a fixed proportion to allocate:

Sga_target = memory_target * 60%

Pga_aggregate_target=memory_target * 40%

B: if Memory_target is not set or = 0 (default is 0 in 11g)

The default value of 0 in 11g cancels the role of Memory_target in the initial state, which is completely consistent with 10g in memory management and is completely backward compatible. (there are also three cases to allocate the size of SGA and PGA)

1) if SGA_TARGET is set, the size of memory space such as shared pool,buffer cache,redolog buffer,javapool,larger pool in SGA is automatically adjusted. PGA depends on the size of the pga_aggregate_target. Sga and pga cannot grow and shrink automatically.

2) neither SGA_target nor PGA_AGGREGATE_TARGET is set

The size of each component in SGA should be clearly set, and the size of each component cannot be adjusted automatically. PGA does not automatically grow and contract.

3) MEMORY_MAX_TARGET setting and MEMORY_TARGET=0 this case is the same as 10g, without explanation, you can use the following values of each component in 11g.

SQL > show parameter targetNAME TYPE VALUE---- archive_lag_target integer 0db_flashback_retention_target integer 1440fast_start_io_target Integer 0fast_start_mttr_target integer 0memory_max_target big integer 1024Mmemory_target big integer 1024Mpga_aggregate_target big integer 0sga_target big integer 0

If you need to monitor the status of Memory_target, you can use the following three dynamic attempts: V$MEMORY_DYNAMIC_COMPONENTS

V$MEMORY_RESIZE_OPS

V$memory_target_advice

Use the following Command to resize:

SQL > ALTER SYSTEM SET MEMORY_MAX_TARGET = 1024M SCOPE = SPFILE;SQL > ALTER SYSTEM SET MEMORY_TARGET = 1024M SCOPE = SPFILE;SQL > ALTER SYSTEM SET SGA_TARGET = 0 SCOPE = SPFILE;SQL > ALTER SYSTEM SET PGA_AGGREGATE_TARGET= 0 SCOPE = SPFILE

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