cancel
Showing results for 
Search instead for 
Did you mean: 

No swaps anyware still hit Ratio around 4% for Initial Record Buffer

Former Member
0 Kudos

Dear Gurus

I am using ABAP NW7.0 System.

in the system all buffers have hit ratio 99+%

but the initial record buffer hit ratio it below 10%

any way there is no swaps at all still hit Ratio is 4%

The current parameters are:

rsdb/ntab/irbdsize --->6000

rsdb/ntab/entrycount---> 20000

HITRATIO -


> % 4

HITS -


> 64

REQUESTS -


> 1.729

DB access quality % -


> 4

DB access -


> 1.656

DB access saved -


> 64

Reorgs -


> 0

Allocated -


> KB 6.625

Available -


> KB 6.000

Used -


> KB 1.099*

Free -


> KB 4.901

Available -


> 5.000

Used -


> 1.656

Free -


> * 3.344*

Objects swapped -


> 0

Frames swapped -


> 0

Total -


> 0

Pl suggest me how can i have the hitratio more.

Thanks in advance

Accepted Solutions (1)

Accepted Solutions (1)

Former Member
0 Kudos

I believe you don't have to do anything in your system as such.

when did you restart your system.?

normally initial record buffers remains lowest among all bufferes .

Watch for swapping and then adjust.

Hope this help.

Amit

Answers (1)

Answers (1)

Former Member
0 Kudos

Hello,

Unfortunately we can not tell exactly why the value is low,

however it is not necessarily an incorrect value.

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.

A more pressing concern would be if we saw swaps on the system. As you

can see, there are no swaps.

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.

Therefore, to conclude, although the hitratio appears low it does

not mean that there are any performance issues. The fact that there is

sufficient free space and there are no swaps confirm this.

You can try to increase size of intial record buffer(in steps) as from current setting it seems to be small.

I hope this helps.

Regards,

Archana

0 Kudos

This is the most clear and concise answer about buffers I´ve ever read! People commonly put a kind of mystery and rules on this subject.

I´m evaluating a system right now where a restart was done one week ago and the Initial records ratio is still 54%. Free space is fine, Free entries is fine, 0 swaps, so everything ok! Nothing to do than wait the buffer be really used and ratio reachs it normal percent.

Thanks Archana!

Hudson Soares