Monitoring sbspaces with onstat -g smb

The onstat -g smb s option displays sbspace attributes.

Use the onstat -g smb s option to display the following characteristics that affect the I/O performance of each sbspace:
  • Logging status

    If applications are updating temporary smart large objects, logging is not required. You can turn off logging to reduce the amount of I/O activity to the logical log, CPU utilization, and memory resources.

  • Average smart-large-object size

    Average size and extent size should be similar to reduce the number of I/O operations required to read in an entire smart large object. The avg s/kb output field shows the average smart-large-object size in kilobytes. In Figure 1, the avg s/kb output field shows the value 30 kilobytes.

    Specify the final size of the smart large object in either of the following functions to allocate the object as a single extent:

    • The DataBlade API mi_lo_specset_estbytes function
    • The Informix® ESQL/C ifx_lo_specset_estbytes function

    For more information about the functions to open a smart large object and to set the estimated number of bytes, see the IBM® Informix ESQL/C Programmer's Manual and IBM Informix DataBlade API Programmer's Guide.

  • First extent size, next extent size, and minimum extent size

    The 1st sz/p, nxt sz/p, and min sz/p output fields show these extent sizes if you set the extent tags in the -Df option of onspaces. In Figure 1, these output fields show values of 0 and -1 because these tags are not set in onspaces.

Figure 1. onstat -g smb s output
sbnum 7    address 2afae48 
  Space    : flags    nchk owner    sbname 
             -------- 1    informix client 

  LO     : ud b/pg flags   flags    avg s/kb max lcks 
           2048    0       -------- 30       -1 
  Ext/IO : 1st sz/p nxt sz/p min sz/p mx io sz 
           4        0        0        -1 

  HdrCache : max   free 
             512   0 

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