onstat -X

Use the -X option to obtain precise information about the threads that are waiting for buffers. For each buffer in use, the -X option displays general buffer information that is also available with either the -b or -B option. For more information, refer to onstat -b in onstat -b.

Example Output

Figure 113. onstat -X Output

    IBM Informix Dynamic Server Version 10.00.UC1 -- On-Line -- Up 18:47:42 -- 34816 Kbytes
        Buffers (Access)
    address  owner    flags pagenum          memaddr  nslots pgflgs scount   waiter  
        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

The onstat -X option has a waiter field to list all user threads that are waiting for the buffer, whereas the onstat -b and -B options contain a waitlist field that displays the address of the first user thread that is waiting for the buffer. The maximum number of shared buffers is specified in the buffers field in the BUFFERPOOL configuration parameter in the ONCONFIG file.

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

flags

Flags identifying the current status of the buffer page:

0x01: Modified Data
0x02: Data
0x04: LRU
0x08: Error
0x20: LRU AIO write in progress
0x40: Chunk write in progress
0x80: Buffer is/will be result of read-ahead
0x100: Cleaner assigned to LRU
0x200: Buffer should avoid bf_check calls
0x400: Do log flush before writing page
0x800: Buffer has been 'buff' -checked
0x8000: Buffer has been pinned
0x10000: Buffer modified by fuzzy operation.

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

scount

Displays the number of threads that are waiting for the buffer

waiter

Lists the addresses of all user threads that are waiting for the buffer