We parallelized a very big index (171GB) creation using this:
SQL> create UNIQUE index PK_TABLE_XXXX ON TABLE_XXXX
(COL1
,COL2
,COL3
,COL4
,COL5)
LOCAL
TABLESPACE TBS_IDX_XXXX
parallel 8
NOLOGGING;
SQL> alter index PK_TABLE_XXXX noparallel;
Unfortunately we went in TEMP tablespace shortage after a couple of minutes of run
Error: ORA-12801 ------------------------------ ORA-12801: erreur signalée dans le serveur de requête parallèle P001, instance xxxxxx(1) ORA-01652: impossible d'étendre le segment temporaire de 128 dans le tablespace TEMP SQL Plan Monitoring Details (Plan Hash Value=762135660) ============================================================================= | Id | Operation | Name | Rows | Temp | | | | | (Estim) | (Max) | ============================================================================= | 0 | CREATE INDEX STATEMENT | | | | | 1 | PX COORDINATOR | | | | | 2 | PX SEND QC (RANDOM) | :TQ10000 | 3G | | | 3 | PX PARTITION HASH ALL | | 3G | | | 4 | INDEX BUILD UNIQUE (LOCAL) | PK_TABLE_XXXX | | | | 5 | SORT CREATE INDEX | | 3G | 32G | --> | 6 | TABLE ACCESS FULL | TABLE_XXXX | 3G | | =============================================================================
This 32GB of maximum TEMP space looks very odd. I have already been working with this data base and I was practically sure that it allows more than this limit. So I looked at the v$sort_segment view:
SQL> compute sum Label 'Total Temp Used' of "Space(GB)" on report
SQL> break on report
SQL> select
*
from
(select
tablespace_name
,inst_id
,round((total_blocks*8192)/(1024*1024*1024),2) "Space(GB)"
from
gv$sort_segment order by 1,2);
TABLESPACE_NAME INST_ID Space(GB)
------------------------------- ---------- ----------
TEMP 1 31.25
TEMP 2 656.22
----------
Total Temp Used 687.47
Notice this 31.25GB of TEMP Space in instance 1. It looks to be closely related to the limit we’ve hit. And, indeed, the index creating script was started from instance 1 as shown in the corresponding Real Time SQL Monitoring report:
Global Information ------------------------------ Status : DONE (ERROR) Instance ID : 1 --> spot this Session : xxxxxx(908:33137) SQL ID : 1h8puyf4b3bw7 SQL Execution ID : 16777216 Execution Started : 01/25/2016 18:02:40 First Refresh Time : 01/25/2016 18:02:40 Last Refresh Time : 01/25/2016 18:04:07 Duration : 87s Module/Action : SQL Developer/- Service : xxxxxx_INST1 Program : SQL Developer
This database is a RAC (11.2.0.3.0) with 2 nodes. It possesses a TEMP tablespace composed with 22 temporary files each of which has 32GB of size. This makes a total available TEMP space of 22*32 = 704GB. Having no clue about the reason for which Oracle has not been able to use the remaining TEMP space from instance 2, i asked to run the same script from instance 2 of the same database:
Global Information ------------------------------ Status : DONE Instance ID : 2 --> second instance Session : xxxxxx(401:717) SQL ID : 1h8puyf4b3bw7 SQL Execution ID : 33554432 Execution Started : 01/26/2016 12:02:59 First Refresh Time : 01/26/2016 12:03:00 Last Refresh Time : 01/26/2016 12:30:07 Duration : 1628s Module/Action : SQL Developer/- Service : xxxxxx_INST2 Program : SQL Developer SQL Plan Monitoring Details (Plan Hash Value=762135660) ============================================================================= | Id | Operation | Name | Rows | Temp | | | | | (Estim) | (Max) | ============================================================================= | 0 | CREATE INDEX STATEMENT | | | | | 1 | PX COORDINATOR | | | | | 2 | PX SEND QC (RANDOM) | :TQ10000 | 3G | | | 3 | PX PARTITION HASH ALL | | 3G | | | 4 | INDEX BUILD UNIQUE (LOCAL) | PK_TABLE_XXXX | | | | 5 | SORT CREATE INDEX | | 3G | 99G | | 6 | TABLE ACCESS FULL | TABLE_XXXX | 3G | | =============================================================================
Notice how the index creation, this time, completes without error, in about 27 minutes and consumes 99GB of TEMP space.
Here’s below the situation of the cached extends in gv$temp_extent_pool view immediately after the index successful creation :
SQL> compute sum Label 'Total Temp Used' of extents_cached on report
SQL> break on report
SQL> select inst_id
, file_id
, extents_cached
, extents_used
from gv$temp_extent_pool
order by 1,2;
INST_ID FILE_ID EXTENTS_CACHED EXTENTS_USED
---------- ---------- -------------- ------------
1 1 31994 8
1 2 4 3
1 3 0 0
1 4 0 0
1 5 3 0
1 6 0 0
1 7 1 0
1 8 0 0
1 9 0 0
1 10 0 0
1 11 0 0
1 12 0 0
1 13 0 0
1 14 0 0
1 15 0 0
1 16 0 0
1 17 0 0
1 18 0 0
1 19 0 0
1 20 0 0
1 21 0 0
1 22 0 0
2 1 0 0
2 2 31995 0
2 3 31999 0
2 4 31999 0
2 5 31996 0
2 6 31999 0
2 7 31998 0
2 8 31999 0
2 9 31999 0
2 10 31999 0
2 11 31999 0
2 12 31999 0
2 13 31999 0
2 14 31999 0
2 15 31999 0
2 16 31999 0
2 17 31999 0
2 18 31999 1
2 19 31999 0
2 20 31999 0
2 21 31999 0
2 22 31999 0
--------------
Total Temp 703973
SQL> select
inst_id,
tablespace_name,
total_blocks,
used_blocks,
free_blocks
from gv$sort_segment;
INST_ID TABLESPACE_NAME TOTAL_BLOCKS USED_BLOCKS FREE_BLOCKS
---------- ------------------------------- ------------ ----------- -----------
1 TEMP 4096256 1536 4094720
2 TEMP 86012288 128 86012160
We have a TEMP tablespace of 22 temporary files in a RAC configuration with 2 nodes. We can point out that, in instance 1, only the first temporary file that has been used. While in instance 2 we see that many extents have been uniformly allocated during the index creation.
SQL> select inst_id, trunc(bytes_cached/1024/1024/1024,2) Gbytes_cached from gv$temp_extent_pool;
INST_ID GBYTES_CACHED
---------- -------------
1 31.24
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
2 0
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
2 31.24
44 rows selected.
Clearly for a reason I am not aware of, Instance 2 is refusing to uncache its temp extents to instance 1. Thanks to Riyaj Shamsudeen I knew that this situation could be due to the bug n° 14383007 which necessitates a patch to be solved.
