onstat -B command: Prints information about used buffers

Use the onstat -B option to display information about buffers that are not on the free-list.

Figure 1: Syntax:

Both onstat -B and onstat -b display the similar information, except that the onstat -b command only displays buffers that are currently being accessed by a user thread. The onstat -B command displays information for all the buffers that are not on the free-list.

For information about running the onstat -B command on a dump file created without the buffer pool, see Running onstat Commands on a Shared Memory Dump File.

Example output

Figure 2: onstat -B command output


Buffer pool page size: 4096

address         userthread flgs pagenum memaddr         nslots pgflgs xflgs owner            waitlist
700000010932fe8 0          806  1:40264 700000011150000 5      8b0    0     0                0
700000010933088 0          806  1:40284 700000011151000 5      870    0     0                0
.
.
700000010933e48 0          806  1:44585 700000011167000 113    8890   0     0                0
700000010933ee8 0          806  1:42578 700000011168000 5      802    0     0                0
700000010933f88 0          86   1:44348 700000011169000 39     890    0     ffffffffffffffff 0
700000010934028 0          6    1:8     70000001116a000 0      1800   0     0                0
7000000109340c8 0          806  1:246   70000001116b000 5      802    0     0                0
.
.
700000010941c28 0          807  1:46486 7000000112ca000 123    801    0     0                0
700000010941ea8 0          806  1:47101 7000000112ce000 10     801    0     0                0
 25 modified, 50000 total, 65536 hash buckets, 4096 buffer size

Output description

Buffer pool page size

the size of the buffer pool pages in bytes

address

the address of the buffer header in the buffer table

userthread

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

the physical page number on the disk

memaddr

the buffer memory address

nslots

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

the user thread that set the xflgs buffer flag

waitlist

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 command: Print thread information.