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ztta/as4/roll_shm_cpp_16MB - size of AS/400 C++ administration area (u. of 16MB)

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| Parameter : ztta/as4/roll_shm_cpp_16MB                               |

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| Short description: Size of AS/400 C++ administration area (u.of 16MB)|

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| Parameter description :                                              |

| -----------------------                                              |

| (See SAP Note 376827)                                                |

| If C++ objects are created on the AS/400 with the new operator,      |

| these are stored on the system heap. On the other hand, C++ offers   |

| the possibility of overriding the new operator and overwriting it    |

| an implementation of your own. In certain places of the SAP code,    |

| this is done, in order to store objects in the SAP roll area rather  |

| than on the heap. If objects instantiated in the roll area in this   |

| way use virtual functions, pointers to a virtual functions table     |

| (vft) are stored in the roll area with the object. As these vfts

| are in the process-local memory of the work process (from a technical|

| point of view, a separate activation group), the roll area therefore |

| contains pointers to the process-local memory.                       |

| If the user is temporarily interrupted during the transaction and is |

| taken out of the work process (rolled out), these pointers are       |

| kept.                                                                |

| If the processing is continued in a different work process, the user |

| receives the same roll area as previously; but with vft pointers that|

| still point to the previous activation group, that is, to the        |

| previous work process. If the system continues to use these pointers,|

| the work process would terminate with an MCH error (illegal pointer).|

| To avoid this type of termination, when the user's transaction is    |

| continued in another work process, SAP attempts to correct these     |

| pointers so that they point to process-local vfts in the new work    |

| process. The prerequisite for this is that the activation groups     |

| (=work processes) are structured identically. SAP puts all places    |

| that could potentially contain vft pointers in the roll area into a  |

| system-wide table in shared memory. The table must include the data  |

| for all users. When a transaction is continued, the data is used to  |

| find all places with vft pointers for the special user and to correct|

| these so that they point to the new work process.                    |

|                                                                      |

|                                                                      |

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| Application Area: System                                             |

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| Unit: Whole number multiples of 16MB                                 |

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| Default value : 5                                                    |

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| Who is permitted to make changes: The customer                       |

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| Restrictions with operating systems: Only OS/400                     |

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| Short Description : size of AS/400 C++ administration area (u. of 16MB) 

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| Applications Area : System 

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| Parameter Type : I 

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| Changes allowed : X 

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| Valid for Operating System : OS400 

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| Dynamic switchable :  

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| Same on all Servers :  

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| Minimum : 1  

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| Maximum : 65536  

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