No free space in directory entries for NTAB buffer

Question

Gurus ,
In ST02 -> for table definitions buffer there was a red alert with the SWAP count as 953275 .
hence i Double clicked on the swaps count to see the details , which is shown below ,
efficiency :
hit ratio  70
size :
allocated : 6799
available  : 5703
used        :5703
free         : 0
Directory entries :
available : 20000
used      : 20000
free        : 0
swaps :
objects swapped : 953833
frames swapped  : 0
what will happen if the 'directory entry '  and 'size' is zero we.
what process will get affected because of this ?
what i need to do next ..
guide me gurus

Answer 1

Hi Susin,
To Answer your question, directory free entries are '0' --> which means table definition buffer is full. That is the reason we can see "objects swapped : 953833"
Try to increase the size of table definition buffer which is low '6799' now.
I feel you can even  double the value and observe the performance.
For General information regarding Hit ratio and Swapping:
The quality of a buffer and how often it is accessed is measured by the
'%Hit Ratio'. This value will indicate if the information stored in the
buffers, such as table entries, programs and screens, is being hit
directly from the buffer itself or, on the other hand, if the system
needs to bring that data from the database since it was not found in the
buffer.
To find out the buffers with poor quality, first check the system
startup time. When the system is started, all buffers (except the
program buffer which has a pre-load) are initially empty. Therefore,
all objects that are accessed for the first time have to be read from
the database and then loaded into the buffers.
If objects are not yet in the buffer, the hit ratio for the buffer will
be low. The hit ratio increases from the time objects are loaded into
the buffers. The rate of the increase depends on the workload in the
system and is different for each buffer.So it is to be noted that how often you restart the system which resuls in the loading of object again and causes hit rate to be low.
Poor buffer quality is not always due to a real problem. For example,
transports into a system can reduce buffer quality. Keep in mind though
that a value lower does not always shows that you have a problem.
Swapping occurs when the buffer is full, and the SAP System has to
load additional objects into the buffer. Objects in the buffer that
were used the least recently are removed. In this context, the term
"swap" means the objects removed from the buffer are lost and cannot
be replaced until a new database access is performed (replacing what
was lost).
There are two possible reasons for swapping
1 There is no space left in the buffer data area
The buffer is too small. You should increase the buffer size.
2 There are no directory entries left.
Hope this helps.
For any other information, feel free to reply me.
Thanks and Regards,
Pavan Kumar Gali.