Storage parameters (storage clause) meaning and setting techniques

Skill system Environment: 1, operating system: Windows 20002, database: Oracle 8i R2 (8.1.6) for NT Enterprise 3, installation path: C:\ORACLE Explanation: Available for: Table space, rollback segment, table, index, partition, snapshot, snapshot log parameter name default value most Small value Maximum Description the INITIAL5 (block) 2 (data block) operating system limits the size of the first extent assigned to segment, in bytes, which cannot be changed in the ALTER statement, and if the specified value is less than the minimum value, the minimum value is created. NEXT5 (Block) 1 (block) operating system limits the second extent size equal to the initial value of Next, next value = previous next size multiplied by (1+pctincrease/100), and if the specified value is less than the minimum value, the minimum value is created. If you change the value of next in the ALTER statement, the next assigned extent will have the specified size, regardless of the extent size and pctincrease parameter values of the last assignment. The MINEXTENTS1 (Extent) rollback segment is a 2 Extent1 (Extent) rollback segment for 2 Extent operating system limits segment the number of Extent assigned on the first creation maxextents based on the size of the Block 1 (Extent) rollback segment is 2 Exten T unrestricted as the amount of data in the segment increases, the maximum number of extent that can be allocated pctincrease50% (Oracle816 0%) 0% the operating system to specify the percentage of the third and subsequent extent relative to the previous extent. If Pctincrease is 0, all newly added extent in segment are the same size, equal to the next value, and if Pctincrease is greater than 0, the value of next is computed each time (with the formula above), and pctincrease cannot be negative. When you create a rollback segment, you cannot specify this parameter, which is fixed to 0 in the rollback segment. OPTIMAL----cannot be smaller than the rollback segment initial allocation space the operating system qualification is only relevant to the rollback segment, and when the rollback segment exceeds the set range of this parameter because of growth, expansion, the Oracle system will dynamically redistribute the extents according to the situation, attempting to reclaim the extent of the multiple allocations. FREELISTS11 block Size limits can only specify freelists and freelist groups parameters in Create TABLE, CLUSTER, index. The number of free lists in each free list group in a Pattern object freelist GROUPS11 Depending on the number of concurrent instances of the OracleThe number of free list groups of database objects created by the user, using this parameter only when using the OPS parallel server option, and one instance for a group. Buffer_pool------------defines the default buffer pool (cache) for a schema object, all of which are stored in the specified cache, and are not valid for tablespaces or rollback segments.
It is recommended that the Pctincrease parameter be set to 0 to minimize fragmentation so that each extent is the same (equal to the next value) once an object is established, its initial and minextents parameters cannot be modified (Oracle Modifiable minextents parameter in 816) any modification to next and pctincrease only affects those that were later allocated extent when assigning a new extent, the system assigns a extent directly to the next value and then uses the formula: previous Next value * (1+pctincrease/100) Calculates the size of the next extent that should be allocated, and saves the results to the Next_extent column of the relevant data dictionary as the next extent size to be allocated. CREATE TABLE Test (a number) STORAGE (INITIAL 100K NEXT 100K minextents 2 maxextents pctincrease 100); Explanation: Initially assign two extent to the test table, the first extent is 100K, because initial=100k the second extent is 100K because next=100k if the data in the table needs to be allocated a third extent, Because the pctincrease is 100, then the third extent is the 200k=100k+100k fourth extent is 400k=200k+200k available through the Data dictionary table dba_tables, All_tables, User_ Tables to view parameter settings, 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