Performance issues and temp errors when accessing the V$LOCK view

Developers report that querying v$lock is particularly slow;

Error in manual execution

[oracle@testdb ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Mon May 7 16:53:19 2018

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL>
SQL>
SQL> select count() from v$lock ;
select count() from v$lock
*
ERROR at line 1:
ORA-01652: unable to extend temp segment by 128 in tablespace TEMP

Query temp usage discovery

TABLESPACE_NAME FREE(G) TOTAL(G) USED(%) FREE(%)

TEMP 0 1 100 0

SQL> SQL>
TOTAL(GB) FREE(GB) TEMP_FILE USED(GB) TOTAL(GB) FREE(GB) USED(GB)

 1        1 /mnt/oradata/xnjc/temp01.dbf          0      1        1           0

All temp is used, and the size of temp table space is only 1G

SQL> SQL> SQL> SQL> 2 3 4 5 6 7 8 9 10 11 12 13 14 15
SID USERNAME TABLESPACE HASH_VALUE SEGTYPE CONTENTS BLOCKS

 8 SEC           TEMP       0/2866845384                   LOB_DATA  TEMPORARY      128

sec user is using temp

The temp table space allocation is too small, solve this allocation problem first

SQL> alter tablespace temp add tempfile '/mnt/oradata/xnjc/temp02.dbf' size 128m autoextend on next 100m
/

Tablespace altered.

The following verify the slow access problem of v$lock

SQL> select count(*) from v$lock ;

COUNT(*)

Access takes more than 30 seconds

View the execution plan under
SQL> SELECT * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT

| 0 | SELECT STATEMENT | | 1 | 50 | 1 (100)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 50 | | |
| 2 | HASH JOIN | | 1 | 50 | 1 (100)| 00:00:01 |
| 3 | MERGE JOIN CARTESIAN | | 100 | 3800 | 0 (0)| 00:00:01 |
| 4 | FIXED TABLE FULL | X$KSUSE | 1 | 19 | 0 (0)| 00:00:01 |
| 5 | BUFFER SORT | | 100 | 1900 | 0 (0)| 00:00:01 |
| 6 | FIXED TABLE FULL | X$KSQRS | 100 | 1900 | 0 (0)| 00:00:01 |
| 7 | VIEW | GV$_LOCK | 10 | 120 | 0 (0)| 00:00:01 |
| 8 | UNION-ALL | | | | | |
| 9 | FILTER | | | | | |
| 10 | VIEW | GV$_LOCK1 | 2 | 24 | 0 (0)| 00:00:01 |
| 11 | UNION-ALL | | | | | |
| 12 | FIXED TABLE FULL| X$KDNSSF | 1 | 64 | 0 (0)| 00:00:01 |

|* 13 | FIXED TABLE FULL| X$KSQEQ | 1 | 64 | 0 (0)| 00:00:01 |

| 14 | FIXED TABLE FULL | X$KTADM | 1 | 64 | 0 (0)| 00:00:01 |
| 15 | FIXED TABLE FULL | X$KTATRFIL | 1 | 64 | 0 (0)| 00:00:01 |

|* 16 | FIXED TABLE FULL | X$KTATRFSL | 1 | 64 | 0 (0)| 00:00:01 |

|* 17 | FIXED TABLE FULL | X$KTATL | 1 | 64 | 0 (0)| 00:00:01 |

|* 18 | FIXED TABLE FULL | X$KTSTUSC | 1 | 64 | 0 (0)| 00:00:01 |

|* 19 | FIXED TABLE FULL | X$KTSTUSS | 1 | 64 | 0 (0)| 00:00:01 |

|* 20 | FIXED TABLE FULL | X$KTSTUSG | 1 | 64 | 0 (0)| 00:00:01 |

|* 21 | FIXED TABLE FULL | X$KTCXB | 1 | 64 | 0 (0)| 00:00:01 |

PLAN_TABLE_OUTPUT

Predicate Information (identified by operation id):

2 - access("SADDR"="S"."ADDR" AND TO_CHAR(USERENV('INSTANCE'))||RAWTOHEX("R
ADDR")=TO_CHAR("R"."INST_ID")||RAWTOHEX("R"."ADDR"))
4 - filter("S"."INST_ID"=USERENV('INSTANCE'))
9 - filter(USERENV('INSTANCE') IS NOT NULL)

PLAN_TABLE_OUTPUT

12 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
13 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
14 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
15 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
16 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
17 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND

PLAN_TABLE_OUTPUT

      "INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)

18 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
19 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
20 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSOBFLG",1)<>0)
21 - filter(("KSQLKMOD"<>0 OR "KSQLKREQ"<>0) AND
"INST_ID"=USERENV('INSTANCE') AND BITAND("KSSPAFLG",1)<>0)

56 rows selected.

With id=3, the Cartesian execution plan estimates the problem. X$KSUSE will not have only one piece of data. The actual query

SQL> select count(*) from X$KSUSE ;

COUNT(*)

SQL> exec dbms_stats.gather_fixed_objects_stats ; gather statistics

do it again

select count(*) from v$lock; solve the problem in seconds

View the adjusted execution plan

Execution Plan

Plan hash value: 2965011029

| 0 | SELECT STATEMENT | | 1 | 36 | 9 (100)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 36 | | |
| 2 | HASH JOIN | | 13905 | 488K| 9 (100)| 00:00:01 |
| 3 | HASH JOIN | | 136 | 3264 | 7 (100)| 00:00:01 |
| 4 | VIEW | GV$_LOCK | 136 | 1632 | 6 (100)| 00:00:01 |
| 5 | UNION-ALL | | | | | |
| 6 | FILTER | | | | | |
| 7 | VIEW | GV$_LOCK1 | 128 | 1536 | 4 (100)| 00:00:01 |
| 8 | UNION-ALL | | | | | |
| 9 | FIXED TABLE FULL| X$KDNSSF | 1 | 16 | 0 (0)| 00:00:01 |
| 10 | FIXED TABLE FULL| X$KSQEQ | 127 | 2159 | 4 (100)| 00:00:01 |
| 11 | FIXED TABLE FULL | X$KTADM | 1 | 16 | 1 (100)| 00:00:01 |
| 12 | FIXED TABLE FULL | X$KTATRFIL | 1 | 14 | 0 (0)| 00:00:01 |
| 13 | FIXED TABLE FULL | X$KTATRFSL | 1 | 14 | 0 (0)| 00:00:01 |
| 14 | FIXED TABLE FULL | X$KTATL | 1 | 26 | 0 (0)| 00:00:01 |
| 15 | FIXED TABLE FULL | X$KTSTUSC | 1 | 14 | 0 (0)| 00:00:01 |
| 16 | FIXED TABLE FULL | X$KTSTUSS | 1 | 16 | 0 (0)| 00:00:01 |
| 17 | FIXED TABLE FULL | X$KTSTUSG | 1 | 14 | 0 (0)| 00:00:01 |
| 18 | FIXED TABLE FULL | X$KTCXB | 1 | 16 | 0 (0)| 00:00:01 |
| 19 | FIXED TABLE FULL | X$KSUSE | 2272 | 27264 | 0 (0)| 00:00:01 |
| 20 | FIXED TABLE FULL | X$KSQRS | 10224 | 119K| 1 (100)| 00:00:01 |

-------------------------------------------------- ------------------------------ Cartesian Execution Plan Elimination------

Summarize:

GATHER_FIXED_OBJECTS_STATS This process collects statistics for all dynamic performance tables

You must have SYSDBA or have ANALYZE ANY DICTIONARY authority to perform this procedure