When you issue an "alter tablespace <TS name> reduce <fixed
value>" command, the tablespace's size (TotalPgs) is reduced in
line with the falling HWM. However, at a point in time, the HWM
may keep decreasing while the TotalPgs variable does not. In the
worst case scenario, this may persist until the HWM cannot be
decreased any more, at which point the tablespace will be
reduced to its target size.
For example, you can issue the command from above, on a
tablespace called USERSPACE with a 4k page size:
"alter tablespace USERSPACE reduce 50 M"
and then monitor the tablespace using db2pd:
"db2pd -db SAMPLE -tablespaces -repeat 2 100"
From the db2pd output below, it is clear that both TotalPgs and
the HWM are initially decreasing. However, TotalPgs stops
decreasing at a value of 80058, while the HWM continues to
decrease. This continues until the HWM hits 52634 (no more free
extents below the HWM), at which point TotalPgs is decreased to
72192 (for a total reduction of 12,800 pages, or 50M).
Address TotalPgs UsablePgs UsedPgs PndFreePgs
FreePgs HWM Max HWM State MinRecTime
NQuiescers PathsDropped
0x07000000416DA6E0 84992 84990 52636 0
32354 83056 83056 0x00000000 1351990976 0
No
0x07000000416DA6E0 82258 82256 52638 0
29618 82170 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80458 80456 52638 0
27818 80382 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52638 0
27418 78354 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52636 0
27420 76350 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52638 0
27418 74316 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52636 0
27420 72350 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52636 0
27420 70414 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52638 0
27418 68450 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52636 0
27420 66706 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52636 0
27420 64894 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52634 0
27422 63326 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52634 0
27422 61368 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52636 0
27420 59380 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52634 0
27422 57448 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52634 0
27422 55312 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 80058 80056 52634 0
27422 53390 83056 0x00080000 1351990976 0
No
0x07000000416DA6E0 72192 72190 52634 0
19556 52634 83056 0x00000000 1351990976 0
No
0x07000000416DA6E0 72192 72190 52634 0
19556 52634 83056 0x00000000 1351990976 0
No |
