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Sybase memory in corresponds to sybase pagesize

Posted on 2013-11-25
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Last Modified: 2013-12-12
I have setup Sybase to use @@maxpagesize 4096, then I just want to confirm the command and formula I used below are correct to convert the value of memory to MB ?

Another strange is our Linux VM is running with 1.8GB memory, I just come across that configure memory is bigger than memory allocated to the VM ?

and the Memory_used is around 6GB ( 3072000 pages ) which we only have 1.8GB memory in Linux VM


> select @@pagesize
2> 
             
 ----------- 
        2048 

(1 row affected)
1> select @@maxpagesize
2> 
             
 ----------- 
        4096 

(1 row affected)
1> sp_configure 'memory'
 
 Parameter Name                                               Default                                  Memory Used            Config Value                             Run Value                                Unit                                     Type                 
 ------------------------------------------------------------ ---------------------------------------- ---------------------- ---------------------------------------- ---------------------------------------- ---------------------------------------- -------------------- 
 additional network memory                                              0                                        0                       0                                        0                             bytes                                    dynamic              
 allocate max shared memory                                             0                                        0                       0                                        0                             switch                                   dynamic              
 compression memory size                                                0                                      152                       0                                        0                             memory pages(2k)                         dynamic              
 engine memory log size                                                 0                                        2                       0                                        0                             memory pages(2k)                         dynamic              
 heap memory per user                                                4096                                  1421312                    4096                                     4096                             bytes                                    dynamic              
 kernel resource memory                                              4096                                     8344                    4096                                     4096                             memory pages(2k)                         dynamic              
 lock shared memory                                                     0                                        0                       0                                        0                             switch                                   static               
 max memory                                                         98304                                  3072000                 1536000                                  1536000                             memory pages(2k)                         dynamic              
 memory alignment boundary                                           4096                                        0                    4096                                     4096                             bytes                                    static               
 memory dump compression level                                          0                                        0                       0                                        0                             number                                   dynamic              
 memory per worker process                                           1024                                        4                    1024                                     1024                             bytes                                    dynamic              
 messaging memory                                                     400                                        0                     400                                      400                             memory pages(2k)                         dynamic              
 pci memory size                                                    32768                                        0                   32768                                    32768                             memory pages(2k)                         dynamic              
 replication agent memory size                                       4096                                     8194                    4096                                     4096                             memory pages(2k)                         dynamic              
 shared memory starting address                                         0                                        0                       0                                        0                             number                                   static               
 total logical memory                                               98304                                   229954                  114973                                   114977                             memory pages(2k)                         read-only            
 total physical memory                                                  0                                   229948                       0                                   114974                             memory pages(2k)                         read-only            
 transfer utility memory size                                        4096                                     8194                    4096                                     4096                             memory pages(2k)                         dynamic              

(1 row affected)
An additional 2842046 K bytes of memory is available for reconfiguration. This is the difference between 'max memory' and 'total logical memory'.
(return status = 1)
1> select 2842046/1024
2> 
             
 ----------- 
        2775 

(1 row affected)
1> select 1536000*2/1024
2> 
             
 ----------- 
        3000 

(1 row affected)
1> select 114973*2/1024
2> 
             
 ----------- 
         224 

(1 row affected)
1> 

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Question by:motioneye
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by:alpmoon
alpmoon earned 334 total points
ID: 39676099
To me it is a bit confusing. Your last calculation is correct. The max memory looks like 224 MB.

But I am not sure where that message is coming from: "An additional 2842046 K bytes of memory is available for reconfiguration. This is the difference between 'max memory' and 'total logical memory'." If this is based on the actual max memory and you have only 1.8 GB memory on Linux box, it may cause a lot of paging.
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by:Joe Woodhouse
Joe Woodhouse earned 166 total points
ID: 39676351
If you run "sp_helpconfig" on a parameter it will tell you the units that sp_configure reports it in.

For most memory-related parameters, sp_configure reports in bytes. I am pretty confident you are only using 224M right now.

The "additional 2842046 K memory is available" is because you have set "max memory" to 3G (note - not 6G). However because "allocate max shared memory" is still set to 0, you haven't requested 3G from the VM because ASE doesn't need it yet.

Your ASE is only using the amount reported by "total mem", i.e. 224M. However if you keep on increasing ASE parameters it will cheerfully allow it up to the "max mem" limit of 3G... and the poor Linux VM will have to try to resource it somehow.
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Accepted Solution

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alpmoon earned 334 total points
ID: 39677528
Joe is totally right. I think I have responded without spending enough time. 224MB is the memory actually used. Max memory is total memory you can allocate. You have configured it as 3000M (actually a bit less than 3GB=3036MB).
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Author Closing Comment

by:motioneye
ID: 39715714
Thanks for the explaination
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