The CEE4ALC allocation strategy type contains attributes that are used to define the characteristics of the storage allocated for heaps. ILE C defines the attributes as shown in CEE4ALC Definition for ILE C. ILE COBOL defines the attributes as shown in CEE4ALC Definition for ILE COBOL, and ILE RPG defines the attributes as shown in CEE4ALC Definition for ILE RPG.
You can define an allocation strategy by altering the attributes of the CEE4ALC allocation strategy type. You do this with the Define Heap Allocation Strategy (CEE4DAS) API. Then, when you use the Create Heap (CEECRHP) API, you can specify the allocation strategy that you defined for the heap attributes you require.
If you use the CEECRHP API, but did not define an allocation strategy, a default allocation strategy provides the heap attributes. See The Default Heap for a description of the default allocation strategy.
Note: The creation size and extension size values of CEE4ALC may be overridden. You do this by specifying values for the initial_size parameter and the increment parameter on the CEECRHP bindable API.
For ILE C the CEE4ALC allocation strategy type is defined as follows:
struct _CEE4ALC {
_INT4 max_sngl_alloc; /* maximum size of a single allocation */
_INT4 min_ddy; /* minimum boundary alignment of any allocation */
_INT4 crt_size; /* initial creation size of the heap */
_INT4 ext_size; /* the extension size of the heap */
_INT2 reserved1; /* must be binary 0 */
_BITS alloc_strat:1; /* a choice for allocation strategy */
_BITS no_mark:1; /* a group deallocation choice */
_BITS blk_xfer:1; /* a choice for block transfer of a heap */
_BITS PAG:1; /* a choice for heap creation in a PAG */
/* The PAG option is ignored in IBM® i */
/* version 5 release 4 and later releases */
_BITS alloc_init:1; /* a choice for allocation initialization */
_UCHAR init_value; /* initialization value */
_BITS reserved2:3; /* must be binary 0 */
_BITS reserved3:32; /* must be binary 0 */
};
For ILE COBOL the CEE4ALC allocation strategy type is defined as follows:
CEE4ALC Definition for ILE
COBOL
01 CEE4ALC-my-own. 05 max-sngl-alloc pic 9(9) BINARY. 05 min-bdy pic 9(9) BINARY. 05 crt-size pic 9(9) BINARY. 05 ext-size pic 9(9) BINARY. 05 reserved1 pic 9(4) BINARY VALUE 0. 05 my-bits pic x VALUE X"E8". * Using initial value of X"E8" , alloc_strat, no_mark, * blk_xfer, and alloc_init are set to TRUE 05 init-value pic x. 05 my-reserved2 pic x(5). 05 my-reserved3 pic x(5).
For ILE RPG the CEE4ALC allocation strategy type is defined as follows:
CEE4ALC Definition for ILE RPG
D CEE4ALC DS D MaxSglAloc 10I 0 D MinBdy 10I 0 D CrtSiz 10I 0 D ExtSiz 10I 0 D res1 5I 0 D AllocBits 1A D InitValue 1A D res2 5A * Use BITON to set on the appropriate bit. * For example BITON AllocInit AllocBits D AllocStrat C '0' D NoMark C '1' D BlkXfer C '2' D PAG C '3' D AllocInit C '4'
Note: If system resources are constrained, the system may override the value specified.
Note: If system resources are constrained, the system may override the value specified.
| 0 | Normal allocation strategy. |
| 1 | Create a process space on each allocation. |
Note: This option should be used only in unusual situations, such as in debugging application problems caused by references past the end of an allocation.
| 0 | Allow the use of the CEEMKHP and CEERLHP APIs. |
| 1 | Do not allow the use of the CEEMKHP and CEERLHP APIs. |
| 0 | Transfer the minimum storage transfer size (that is, 1 storage unit). |
| 1 | Transfer the machine default storage transfer size (that is, 8 storage units). |
Note: On the reduced instruction set computer (RISC) hardware, this parameter has no effect. Regardless of whether 0 or 1 is specified for blk_xfer, the machine default storage transfer size will always be transferred.
| 0 | Do not create the heap in the PAG. |
| 1 | Create the heap in the PAG. |
Note: It is possible for the PAG to overflow, at which point any requested PAG heap creations or extensions will not reside in the PAG. Therefore, the system may ignore the request to create the heap in the PAG.
Note: The PAG option is ignored in IBM i version 5 release 4 and later releases.
| 0 | Do not initialize the heap with Init_Value. |
| 1 | Initialize the heap with Init_Value. |
From the programmer's viewpoint, a default heap is always available in the activation group. In fact, the first request to allocate storage results in the creation of the default heap from which the storage allocation takes place.
The attributes of the default heap are defined by the system through a default allocation strategy. You cannot change this default allocation strategy. Following is an example of the default allocation strategy:
Max_Sngl_Alloc = 16MB - 64KB
Min_Bdy = 16
Crt_Size = 4KB
Ext_Size = 4KB
Alloc_Strat = 0
No_Mark = 1
Blk_Xfer = 0
PAG = 0
Alloc_Init = 0
Init_Value = 0x00 /* This value is not used */
/* if Alloc_Init is 0 */
In addition, the default heap in an activation group has the following special characteristics:
Languages that do not have an intrinsic multiple-heap storage model (such as ILE C) use the default heap. This heap cannot be discarded and is immune to the Mark Heap (CEEMKHP) and Release Heap (CEERLHP) APIs. Storage allocated within the default heap can be freed only by explicit free operations or when the owning activation group ends.
This implementation ensures that the storage is not inadvertently released in mixed-language applications. Release heap and discard heap operations are considered insecure for the following reasons:
If release heap operations were valid for the default heap, then procedures that correctly use different storage management capabilities separately might fail when used in combination.
[ Back to top | ILE CEE APIs | APIs by category ]