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onstat -g dic Data dictionary cache

The onstat -g dic command displays the tables whose data dictionary information is currently stored within the dictionary cache in memory.

Dictionary Cache:  Number of lists: 31, Maximum list size: 10                  
list#  size  refcnt  dirty?  heapptr        table name                         
   1     3      1      no     14b5d890   wbe@oninit_shm:informix.t0010url      
                1      no     14cbb820   wbe@oninit_shm:informix.t9051themeval 
                0      no     14b63c20   wbe@oninit_shm:informix.t0060hits     
   2     2      0      no     14b97420   wbe@oninit_shm:informix.t0120import   
                1      no     14b6c820   wbe@oninit_shm:informix.t9110domain   
   3     3      0      no     14bce020   wbe@oninit_shm:informix.t0150url      
                0      no     14d3d820   contact@oninit_shm:informix.wbtags    
                0      no     14c87420   wbe@oninit_shm:informix.wbtags        
   4     1      0      no     14b7a420   drug@oninit_shm:viagra.product        
Total number of dictionary entries: 36      

Output Description

Heading Description Format
list# The data dictionary hash chain ID Dec
size The number of entries in this hash Dec
refcnt The number of SQL statements currently referencing one of the entries in this cache. Dec
dirty? Whether this entry has been modified relative to its entry on disk. Str
heapptr The in-memory address for the heap used to store this entry. Hex
table name The name of the table in the cache. Str

The onstat -g dic command can also take a tablename. This can be very useful when tracking down indices, constraint ID etc without using SQL

IBM Informix Dynamic Server Version 14.10.FC3DE -- On-Line -- Up 00:04:28 -- 299964 Kbytes

Dictionary entry for table: latency1 [hashes to list#: 28]

ddt_tabfullname: eric@strider_net:informix.latency1
ddt_partnum:    1049059 ddtab-address:  5480c058
ddt_fextsize:   16      ddt_nextsize:   16      ddt_locklevel:  1
ddt_flag:       -2147483648     ddt_flag2:      33554432        ddt_ps:         0       ddt_row:        5480c038
ddt_dbalthash:  10      ddt_dbaltcount:         178     ddt_ncols:      2
ddt_rowsize:    15      ddt_nallidxs:   1       ddt_nindexes:   1       ddt_type:       T
ddt_nrows:      1       ddt_npused:     1       ddt_tabid:      142
ddt_majversion: 145     ddt_minversion: 58      ddt_perms:      5480c9b0
Table Permissions:
Userthread  has 
Userthread  has 
ddt_cols:       5480c460        ddt_indexes:    5480c248        ddt_uniq:       5480cb60
ddt_ref:        0       ddt_check:      5480ca40        ddt_dummytab:   5480c560
ddt_secpolicyid:        0       ddt_protgranularity:    -
ddt_rowver_pos:         0       ddt_rowchk_pos:         0
ddt_nopcls:     0       ddt_opcls:      0       ddt_numreftabs: 0
ddt_reftabs:    0       ddt_next:       53f96858        ddt_prev:       547ef058
ddt_refcount:   1       ddt_frags:      0
ddt_fraghdr:    0
ddt_viotid:     0
ddt_diatid:     0

Column Descriptors:
ddc_name:       id      ddc_colno:      1       ddc_default:    0
ddc_flags:      8388608 ddc_type:       262     ddc_xid:        0       ddc_start:      0
ddc_len:        4       ddc_nunique:    1       ddc_next:       5480c4e0
ddc_name:       ins_dte ddc_colno:      2       ddc_default:    0
ddc_flags:      0       ddc_type:       10      ddc_xid:        0       ddc_start:      4
ddc_len:        4879    ddc_nunique:    0       ddc_next:       0

Index Descriptors:
ddil_name:      pk_latency1     ddil_keylen:    4       ddil_flags:     34824
ddil_next:      0       ddil_colno:     { 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 }
ddil_count: 1   ddil_frags:     5481ab08
lf_nfrags:      1       lf_strategy:    1 (none)
lf_afrag:       5481ac28        lf_fragpart:    0       lf_collist:     0
Fragment# 1     lf_frag:        5481ab78
lf_flags:       0       lf_fragid:      1049065
lf_loc: rootdbs
lf_ploc: rootdbs
lf_expr:        0       lf_linexpr:     0       lf_linsize:     0
lf_levels/clust: 1/0    frag_leaves/nunique:    1/1
ddil_state:     E
ddil_collation:         en_US.819

Referential Constraints:

Unique Constraints:
ddc_constrid:   46      ddc_owner:      informix        ddc_name:       pk_latency1
ddc_type:       P       ddc_flags:      0       ddc_uindex:     5480c248
ddc_urefc:      0       ddc_selfrefcnt: 0
ddc_colnml:     { id }
ddc_state:      E
ddc_collation:  en_US.819

Check Constraints:
ddc_constrid:   45      ddc_owner:      informix        ddc_name:       n142_45
ddc_type:       C       ddc_flags:      64      ddc_checkexp:   5480cf80
ddc_checktxt:      ddc_txtsize:    0
ddc_colnml:     { }
ddc_state:      E
ddc_collation:  en_US.819
ddc_constrid:   46      ddc_owner:      informix        ddc_name:       pk_latency1
ddc_type:       C       ddc_flags:      32      ddc_checkexp:   5480ccd0
ddc_checktxt:      ddc_txtsize:    0
ddc_colnml:     { }
ddc_state:      E
ddc_collation:  en_US.819

ddtr_trigid:    8       ddtr_owner:     informix        ddtr_name:      trg_latency1
ddtr_type:      I
ddtr_trigcol:   { }
ddtr_ptree:     54841168
ddtr_state:     E
ddtr_collation:         en_US.819

1 entries found.

Note: the table can have multiple entries, typically 1 clean and multiple dirty.

There are other operations beyond DDL that will cause a data dictionary entry to be marked as dirty. An example is any update statistics operation. A dirty entry will remain visible in the cache until all references to the cache entry have been removed. Any active SQL statement against a table will generate a reference to that table's data dictionary cache entry, as will declared cursors and stored procedures. Since ER has to know about the structure of a table in order to know how to interpret logical log records then it's likely it will also hold a reference to the dictionary cache.

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