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Overflow of the export/import buffer

Updated May 18, 2018

Transaction ST02 displays a high number of swaps relating to the export/import buffer.

With the aid of transaction ST02, you can display buffer sizes and buffer behavior. In the detail screen for the export/import buffer, you can read under 'Swaps' how many objects (objects swapped) and how many blocks (Frames swapped) were deleted from the export/import buffer since system restart.The objects that have not been used for the longest are deleted. Deletions are quite usual if there are competing applications for the export/import buffer.This becomes a high-priority performance factor if the buffer has no time to do anything but load and displace objects.
As of Release 4.6B, the ABAP List Viewer (ALV) uses the export/import buffer to improve performance. The objects written by the ALV to the export/import buffer are not removed automatically again from the buffer, but are retained in the buffer until the system shuts down.This is what is supposed to happen, since it is assumed that users repeatedly use the ALV and the objects can be read at high speed from the buffer.ALV objects can also be removed explicitly from the buffer using a program if data structures are changed.
An increased number of swaps can occur if several applications use the import/export buffer or if the buffer size selected is too small.

Solution 1:

Note that the number specified under 'Swaps' is the total number of swaps since the system start. This number can become very high if your system has been running for a long time.
If these swaps occur during the availability check, then refer to note 99999.
A high number of swaps is only a problem if the buffer has no time to do anything other than load and displace objects. You can recognize this situation from the buffer hit ratio. You can use transaction ST02 to determine the hit ratio. The hit ratio should be higher than 80 %. If it is lower than this, proceed as described in solution 2.

Solution 2:

Use transaction ST02 to check your buffer settings for the export/import buffer:
'Size' indicates the size of the buffer in kB.'Free' displays how much space is still free.If possible, 10 % of the total buffer size should be kept free.Using the profile parameter 'rsdb/obj/buffersize', you can define the size of the export/import buffer in kB.
'Directory entries ' specifies the maximum number of the objects that can be buffered.The number of free directories should also be about 10 % of the total number.The profile parameter 'rsdb/obj/max_objects' defines the number of the buffer objects.
When increasing the buffer parameters in the SAP profile, note the following:

        a) Your system must have enough main memory so that it does not switch to swapping.

        b) It is impossible to set forth absolute guide values for optimal buffer size.The sizes depend on the update level, amount of data in the system and the applications used.The figures given in this note are to be taken as rough indicators only. However, the buffer must at least be large enough to admit the administrative information of all buffer objects, that is, it must always be larger than 'rsdb/obj/max_objects' multiplied by 200 bytes;otherwise the instance cannot be powered up.

        c) To implement the profile change, you must restart the system.

        d) After successful adjustment, it is recommended that you check the buffer after some time using transaction ST02.