System environment:
1. Operating system: Windows 20002, Database: Oracle 8i R2 (8.1.6) for NT Enterprise Edition 3, Installation Path: C: / Oracle
Explanation:
Can be used: table space, rollback segments, table, index, partition, snapshot, snapshot log
Parameter Name Default Value Maximum Value Description Initial5 (Data Block) 2 (Data Block) Operating System Limits the size of the first extent of the Segment, in bytes, this parameter cannot be changed in the ALTER statement, if The specified value is less than the minimum, then created by minimum value. Next5 (Data Block) Operating System Limits the second EXTENT size equal to the initial value of Next, the next NEXT value = the previous NEXT size multiplied (1 pctincrease / 100), if the specified value is less than the smallest Value, create it by minimum. If the value of NEXT is changed in the Alter statement, the next assigned extent will have the specified size regardless of the previously assigned extent size and the PctincRease parameter value. Minelt1 (Extent) Rolling Segment For 2 Extent1 (Extent) Rolling Segments for 2 Extent Operating System Limited Segment Operations EXTENT Number MaxExtTS MaxExtents MaxExtent Square, depending on the size of the data block 1 (Extent) rollback segment 2 EXTENT unlimited With the increase in data volume in segment, the maximum allocated extent number Pctincrease50% (0% in Oracle816) 0% operating system defines the specified third and its subsequent EXTENT is added relative to the previous extent. Percentage, if pctincrease is 0, all newly added extents in segment are the same size, equal to NEXT values, if PctinCRease is greater than 0, calculate the value of NEXT (with the above formula), Pctincrease cannot be negative. This parameter cannot be specified when creating a rollover segment, and this parameter is fixed to zero. Optimal ---- Do not be smaller than the initial allocation space operating system of the rollback segment is only related to the rollback segment, when the segment exceeds the setting range of this parameter due to growth, the ORACLE system is dynamically redistributed according to the situation Extents, trying to recover the multi-allocated extent. FreeLists11 Data block size can only specify freeelists and freeelist groups parameters in Creelists, Cluster, Index. The number of free lists in each free list group in the mode object is the number of free list groups of the database object created by the number of user parallel instances of the Oracle parallel instance, only using this parameter when using the OPS parallel server option, one instance corresponds to A group. Buffer_pool ---------- Defines the Mode Object Definition Default Buffer Pool (Cache), which is stored in the specified cache, which is invalid for tablespace or rollback segments.
It is recommended that the PctinCrease parameter is set to 0, minimizing the fragment, so that each extent is the same (equal to the NEXT value)
Once an object is established, its initial and mineltents parameters cannot be modified (MINEXTENTS parameters can be modified in Oracle 816)
Any modification of next and pctincrease only affects those of the subsequent assigned
When allocating a new extent, the system is allocated to the value of NEXT, then uses the formula: the previous NEXT value * (1 pctincrease / 100) calculates the size of the extent that should be assigned,
And save the calculation to the NEXT_EXTENT column of the relevant data dictionary, as the size of the Extent, which should be assigned.
Create Table Test (a Number)
STORAGE
Initial 100K
Next 100k
Minextents 2
MaxExtents 100
PctinCrease 100);
Explanation:
Initially assigned two extents to the TEST table,
The first extent is 100K, because initial = 100k
The second EXTENT is 100K, because Next = 100K
If data is increased due to data, the third extent is needed, because Pctincrease is 100, then
The third EXTENT is 200K = 100k 100K
The fourth extent is 400K = 200K 200K
You can view parameter settings by data dictionary tables DBA_TABLES, ALLs, User_Tables, such as:
SELECT TABLE_NAME, INITIAL_EXTENT, NEXT_EXTENT, MIN_EXTENTS, MAX_EXTENTS, PCT_INCREASE from User_Tables;
TABLE_NAME INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE
---------- -------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------
TEST 106496 212992 2 100 100
