Monitoring Loads and Unloads of Data

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Monitoring Loads and Unloads of Data

You can use the following tools to monitor the load of simple large objects and other data from named pipes:

SET EXPLAIN ON output
onstat -g xqs

Using SET EXPLAIN ON Output

To obtain the information that Figure 85 shows, you can issue the SET EXPLAIN ON statement prior to the INSERT statement to load a simple large object:

The xlread fields show the number of xlread SQL operators on each coserver. If the data is in fixed or delimited format, the rows_read field represents the number of 34-kilobyte buffers that xlread has read.
The rows_rej fields show the number of rows that were rejected during the load.
The xlcnv field shows information about the number of rows that the xlcnv (load converter) has converted and read. If the data is in Informix format, no data displays in the xlcnv field because no load converter operator is created.
In the XMP Query Plan section, the width field is the total number of iterator instances on all coservers.
The XMP Query Statistics section shows how these instances are laid out on the coservers and how many rows each instance produces.

Figure 85. SET EXPLAIN Output During the Load of Simple Large Objects

XMP Query Plan

oper    segid  brid  width
--------------------------
xlread  2      0     2
xlcnv   2      0     2
insert  1      0     1

XMP Query Statistics

type    segid  brid  information
--------------------------------
xlread  2      0     inst cosvr time  rows_read  rows_rej
                     ---- ----- ----  ---------  --------
                     0    2     8     23         0
                     1    1     9     23         0
                     --------------------------------------
                     2                46         0

xlcnv  2      0      inst cosvr time  rows_converted rows_rej
                     ---- ----- ----  -------------  --------
                     0    2     8     20004          0
                     1    1     9     20004          0
                     --------------------------------------
                     2                40008          0

insert 1      0     inst  cosvr time  it_count
                    ----  ----- ----  --------
                    0     1     8     40008
                    ---------------------------
                    1                 40008

Using onstat to Monitor Pipe Staging

While the INSERT statement is executing to load simple large objects, you can use the onstat -g xqs command to display the following statistics:

Number of actual xlread SQL operators currently executing on each coserver
Number of rows read and number of rows rejected by each xlread SQL operator

Because the onstat -g xqs command gathers statistics periodically, the output might not be accurate. For more information on interpreting the statistics, see your IBM Informix: Performance Guide. Figure 86 shows sample output for onstat -g xqs that is similar to the SET EXPLAIN output in Figure 85.

Figure 86. onstat -g xqs Output

type   segid  brid  information
----   ----   ----  -----------
xlread 2      0     inst cosvr time rows_read rows_rej
                    ---- ----- ---- --------- --------
                    0    2     4    16        0
                    1    2     5    14        0
                    -----------------------------------
                    2               30        0

insert 1      0     inst cosvr time it_count
                    ---- ----- ---- --------
                    1    2     4    15
                   -------------------------
                    2               15