no free space in directory entries for NTAB buffer

[Former Member]

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

[pavan_kumargali · Accepted solution]

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.

[Former Member]

HI

Your system needs performance tunning, there are many parameters are related to each other which need to set according to hardware and workload.

eg:-

rsdb/ntab/sntabsize xxxx Size of short nametab

rsdb/ntab/entrycount xxxx Max. number / 2 of entries buffered

I will advise you to set the EarlyWatch check to get the SAP Recommendation on the following areas;

System Configuration

System Performance

Workload Distribution

SAP System Operating

Database Administration

Authorization Checks

SAP also recommending to set the EWC on each 6 months to revise the SAP REcommendations.

Regards

Anwer Waseem

SAP NetWeaver

[Former Member]

Thanks a lot for your reply .

we also have a problem in EWA for past 3 months . there are no EWA reports in our inbox since may first .

i also need to ask you one more thing .

EWC also will be sent as a report like EWA ?

because i just want to find have we received any EWC so far ?

[Former Member]

can anyone please explain what is the effect of 'directory free entries ' having 0 .

what is the purpose and use of that

[Former Member]

Hi

Yes both reports are typicall, EWA is automated service which give you the alert of the system but EWC session should be performed by SAP Engineer to get the SAP best recommendation.

Regards

Anwer Waseem