onstat -b

The -b option displays information about buffers currently in use, including the total number of resident pages in the buffer pool. (For information about all buffers, not just those in use, use onstat -B.)

The maximum number of buffers available is specified in the buffers field in the BUFFERPOOL configuration parameter in the ONCONFIG file.

The -b and -B options also provide summary information about the number of modified buffers, the total number of resident pages in the buffer pool, the total number of buffers available, the number of hash buckets available, and the size of the buffer in bytes (the page size).

Example Output

Figure 32. onstat -B Output

    IBM Informix Dynamic Server Version 10.00.UC1       -- On-Line -- Up 18:35:04
 -- 34816 Kbytes    
    Buffers
    address  userthread flgs pagenum       memaddr  nslots pgflgs xflgs owner   waitlist
    
    Buffer pool page size: 2048
     0 modified, 3000 total, 4096 hash buckets, 2048 buffer size
    
    Buffer pool page size: 8192
     0 modified, 1000 total, 1024 hash buckets, 8192 buffer size

Output Description

You can interpret output from the -b and the -B options as follows:

Buffer pool page size

is the size of the buffer pool pages in bytes

address

Is the address of the buffer header in the buffer table

userthread

is the address of the most recent user thread to access the buffer table. Many user threads might be reading the same buffer concurrently.

flgs

Uses the following flag bits to describe the buffer:

0x01: Modified data
0x02: Data
0x04: LRU
0x08: Error

pagenum

Is the physical page number on the disk

memaddr

Is the buffer memory address

nslots

Is the number of slot-table entries in the page

This field indicates the number of rows (or portions of a row) that are stored on the page.

pgflgs

Uses the following values, alone or in combination, to describe the page type:

1: Data page
2: Tblspace page
4: Free-list page
8: Chunk free-list page
9: Remainder data page
b: Partition resident blobpage
c: Blobspace resident blobpage
d: Blob chunk free-list bit page
e: Blob chunk blob map page
10: B-tree node page
20: B-tree root-node page
40: B-tree branch-node page
80: B-tree leaf-node page
100: Logical-log page
200: Last page of logical log
400: Sync page of logical log
800: Physical log
1000: Reserved root page
2000: No physical log required
8000: B-tree leaf with default flags

xflgs

Uses the following flag bits to describe buffer access:

0x10: share lock
0x80: exclusive lock

owner

Is the user thread that set the xflgs buffer flag

waitlist

Is the address of the first user thread that is waiting for access to this buffer

For a complete list of all threads waiting for the buffer, refer to onstat -X.