Home > tips > Using Index Unusable For Gaining Disk Space In Partitioned Tables

Using Index Unusable For Gaining Disk Space In Partitioned Tables


Why dedicate disk space for indexes that you are not using for data access in older partitions.

–index partition usable

select * from ADMIN1.RNC_CELLSTATS_DERYA_CFO where datetime=to_date(‘31.10.2011 23:45:00′,’dd.mm.yyyy hh24:mi:ss’)

Plan
SELECT STATEMENT ALL_ROWS Cost: 43.447 Bytes: 667.772.937 Cardinality: 79.677 CPU Cost: 1.219.929.850 IO Cost: 43.396 Time: 2
3 PARTITION RANGE SINGLE Cost: 43.447 Bytes: 667.772.937 Cardinality: 79.677 CPU Cost: 1.219.929.850 IO Cost: 43.396 Time: 2 Partition #: 1 Partitions accessed #1
2 TABLE ACCESS BY LOCAL INDEX ROWID TABLE ADMIN1.RNC_CELLSTATS_DERYA_CFO Object Instance: 1 Cost: 43.447 Bytes: 667.772.937 Cardinality: 79.677 CPU Cost: 1.219.929.850 IO Cost: 43.396 Time: 2 Partition #: 2 Partitions accessed #1
1 INDEX RANGE SCAN INDEX (UNIQUE) ADMIN1.RNC_CELLSTATS_DERYA_CFO_PK Search Columns: 1 Access Predicates: “DATETIME”=TO_DATE(‘ 2011-10-31 23:45:00’, ‘syyyy-mm-dd hh24:mi:ss’) Cost: 159 Cardinality: 79.677 CPU Cost: 17.926.550 IO Cost: 158 Time: 1 Partition #: 3 Partitions accessed #1

–index partition unusable, after

ALTER INDEX ADMIN1.RNC_CELLSTATS_DERYA_CFO_PK

MODIFY PARTITION P20111031

UNUSABLE;

select * from ADMIN1.RNC_CELLSTATS_DERYA_CFO where datetime=to_date(‘31.10.2011 23:45:00′,’dd.mm.yyyy hh24:mi:ss’)

Plan
SELECT STATEMENT ALL_ROWS Cost: 257.057 Bytes: 667.772.937 Cardinality: 79.677 CPU Cost: 2.924.946.617.725 IO Cost: 135.767 Time: 9
2 PARTITION RANGE SINGLE Cost: 257.057 Bytes: 667.772.937 Cardinality: 79.677 CPU Cost: 2.924.946.617.725 IO Cost: 135.767 Time: 9 Partition #: 1 Partitions accessed #1
1 TABLE ACCESS FULL TABLE ADMIN1.RNC_CELLSTATS_DERYA_CFO Object Instance: 1 Filter Predicates: “DATETIME”=TO_DATE(‘ 2011-10-31 23:45:00’, ‘syyyy-mm-dd hh24:mi:ss’) Cost: 257.057 Bytes: 667.772.937 Cardinality: 79.677 CPU Cost: 2.924.946.617.725 IO Cost: 135.767 Time: 9 Partition #: 2 Partitions accessed #1

–other partitions goes over indexes (usable index partitions) Beware that, if you are using bind variables, you may go with FTS over indexed partitions. You may use hints for a solution for access path, like INDEX(CELLHANDOVERS CELLHANDOVERS_PK).

 

select * from ADMIN1.RNC_CELLSTATS_DERYA_CFO where datetime=to_date(‘01.11.2011 23:45:00′,’dd.mm.yyyy hh24:mi:ss’);

Plan
SELECT STATEMENT ALL_ROWS Cost: 1.810 Bytes: 24.472.520 Cardinality: 2.920 CPU Cost: 50.591.850 IO Cost: 1.808 Time: 1
3 PARTITION RANGE SINGLE Cost: 1.810 Bytes: 24.472.520 Cardinality: 2.920 CPU Cost: 50.591.850 IO Cost: 1.808 Time: 1 Partition #: 1 Partitions accessed #2
2 TABLE ACCESS BY LOCAL INDEX ROWID TABLE ADMIN1.RNC_CELLSTATS_DERYA_CFO Object Instance: 1 Cost: 1.810 Bytes: 24.472.520 Cardinality: 2.920 CPU Cost: 50.591.850 IO Cost: 1.808 Time: 1 Partition #: 2 Partitions accessed #2
1 INDEX RANGE SCAN INDEX (UNIQUE) ADMIN1.RNC_CELLSTATS_DERYA_CFO_PK Search Columns: 1 Access Predicates: “DATETIME”=TO_DATE(‘ 2011-11-01 23:45:00’, ‘syyyy-mm-dd hh24:mi:ss’) Cost: 7 Cardinality: 2.920 CPU Cost: 749.500 IO Cost: 7 Time: 1 Partition #: 3 Partitions accessed #2

Unique constraint also worked for usable index partition.       

Inserting same row in the range usable index triggered below error:

ORA-00001: unique constraint (ADMIN1.RNC_CELLSTATS_DERYA_CFO_PK) violated

Only thing to remember is: DML activity on unusable partitions is impossible, without rebuilding the index!

Inserting existing row, which must trigger unique constraint, gives unusable state error:

insert into ADMIN1.RNC_CELLSTATS_DERYA_CFO(datetime,rnc,cell) values (to_date(‘31.10.2011 23:45:00′,’dd.mm.yyyy hh24:mi:ss’),’KRP1R01′,’YUNUP32′);

ORA-01502: index ‘ADMIN1.RNC_CELLSTATS_DERYA_CFO_PK’ or partition of such index is in unusable state

Inserting non-existent row, which must not trigger unique constraint, also gives  unusable state error:

insert into ADMIN1.RNC_CELLSTATS_DERYA_CFO(datetime,rnc,cell) values (to_date(‘31.10.2011 23:44:00′,’dd.mm.yyyy hh24:mi:ss’),’KRP1R01′,’YUNUP32′);

ORA-01502: index ‘ADMIN1.RNC_CELLSTATS_DERYA_CFO_PK’ or partition of such index is in unusable state

In a 1TB sized table RNC_CELLSTATS, making unusable frees 15 GB. Thus, you may not gain big spaces from big tables. While selecting targets  focus on index segments having huge sizes.

SEGMENT_NAME GB # partitions
RNC_CELLSTATS

980

91

RNC_CELLSTATS_PK

15

91

Below, focusing on index segments sizes over 100G, you may earn 6 TB disk space. Data is extracted by using DBA_SEGMENTS dictionary view.

SEGMENT_NAME Size GB # partitions Earned GB
CELLHANDOVERS_PK

2.666

1.100

2132

CELLHANDOVERS_IND1

859

1.100

686

CELLHANDOVERS_IND3

819

1.100

654

CELLHANDOVERS_IND2

811

1.100

648

SGSN_CDR_NDX03

725

65

362

RNC_CELLHO_PK

311

91

155

MGW_E1TTP_PK

271

91

216

RNC_GSMRELATION_PK

245

91

122

CELLIDENTITY_NDX

228

65

114

RNC_CELLHO_PK2

208

91

103

RECORDOPENINGDATE_NDX

193

65

96

INTERNAL_SOHO_DS_MISSING_NE_IX

188

31

93

ENUM_FULL_IND01

161

180

128

MGW_E1TTP_D_PK

146

91

72

NEIGHBOUR_CELL_PK

128

100

63

CELLHANDOVERS_CL_PK

123

1.100

98

CCNPERFCOUNTER_PK

122

31

60

MGW_TDMTERMGRP_PK

109

91

54

CELLHANDOVERS_CL_IND2

102

1.100

81

6,280

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