The main memory parameter is CACHE_SIZE - which is a number of 8 kb pages. On top there comes the CAT_CACHE_SUPPLY plus various smaller buffers for the user tasks.
> so suppose CACHE_SIZE=50000, my main memory will be bytes=50000/8. Will Maxdb only consumes less memory.
Nope - MaxDB will allocate as much memory for the cache as you told it to.
Therefore, if your main memory is just as big as your configured cache size, you will see paging for the kernel process, since it needs to use other areas of memory as well.
You may query the view MEMORYALLOCATORSTATISTICS to figure out how much memory has been allocated by the instance. But be carefull as the rows in this table cannot be simple added up, as there is a hierarchical dependence between the different allocator types.
Check note 1128916 FAQ: MaxDB/liveCache Heap-Management for more details on this.
But Memory allocator shows SystemHeap has 5G, but the physical memory on the box is 5G. Thats doesn't match since my sap is also running on the same box.
I'm trying to find how much sap is using & DB is using
> But Memory allocator shows SystemHeap has 5G, but the physical memory on the box is 5G. Thats doesn't match since my sap is also running on the same box.
Well, it does not have to match.
Ever heard of virtual memory?
That's what's used by your system to provide all the required memory to SAP and MaxDB.
I assume that your system is heavily paging...
> I'm trying to find how much sap is using & DB is using
Well, for the database you've already found the info.
> But again how to find out how much of my physical memory is used by DB. Out of 5G suppose say it uses 2 G of physical memory & 3 G of virtual .
>
> How to find that.
Depends on your operating system.
This is something that only the operating system knows and manages.
It is totally transparent to the processes.
On UNIX/Linux you may check ps or top commands, on Windows the taskmanager or the sysinternals process monitor should do.
In any case, the goal has to be that the database process memory is always kept in RAM and never paged. Otherwise the DB Cache wouldn't make much sense, would it?
The database 'knows' better, which data to keep in memory and which to put back to disk than the operating system does.
Therefore: better have a smaler DB cache but be sure that this one fits into your RAM.
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