Introduction to ALLIDS Threshold and Modify Method for ODSEE and DSEE
Last updated on MARCH 05, 2018
Applies to:Oracle Directory Server Enterprise Edition - Version 6.3.1 SP1 DPS220.127.116.11 and later
Information in this document applies to any platform.
Many Customers want to increase the allidtreshold
but the question is always which value can I use ?
Definition: all-ids-threshold / allidsthreshold
This property defines the maximum number of values per index key that the server maintains in an index list. It can be set for an entire server instance, for an entire suffix, and for anindividual attribute type. You can also set individual thresholds for equality, presence, and substring indexes.
Customer would like to raise the allid threshold and need further information regarding the documentation-recommended soft limit of 50.000.
The most important trees are:
ou=people ~ 200.000 Entries, flat structure
ou=people ~ 80.000 Entries, flat structure
ou=people ~ 70.000 Entries, flat structure
ou=people ~ 20.000 Entries, flat structure
ou=groupofurls ~ 2.000 Entries, flat structure
... some more minor ou's
Our directory is mature, number of entry growth is ~ 1%/year
It's very important to found the good sizing of allidsthreshold:
If the index of one of the specified attributes matches too many entries (ALLIDs), the search becomes non-indexed (notes=U in the access log), and If the value of allidsthreshold is too high, you lost the benefit of the index, the search scan too many entries and the performances are near a search non-indexed.
The Reference Guide says about allidsthreshold:
"You should avoid setting the threshold above 50 000, even for very large deployments.However, you might set all-ids-threshold to a value other than the 5% guideline in the following situations:
set the all-ids-threshold high for parent and ancestor indexes so that all entries below a given branch are indexed."
This magical "50.000" limit has been around since Version 5 and we would like to know, if we can raise the allidsthreshold above 50.000 to a target value of 250.000.
- We have several clients regularly search one of the mentioned subtrees to get a list of the contained DNs (hitting the allid-threshold limit of ancestor/parent index).
- We have several clients regularly search for all members of certain groupOfURLs-groups with ~150.000 members (we have about 50 groupOfURLs with ~100.000 members)
We could really need such a SEARCH speedup and would now like to know if 250.000 would be ok as global allidsthreshold, and only keep all substring-indexes thresholds to 4000.
The "50.000" limit has been around since years (Version 5) and there also has been vast hardware improvements since then.
There is no clear documentation what will happen if this soft limit of 50.000 is exceeded.
- no 50 000 is not a limit, the limit is near 250 000 but it depends of the size of the db_size_page ...
- normally if the candidate list ( allidsthreshold) > 20 % ~ 50% of the number of entries in your database, probably in majority of cases you will lost the index benefit but it should depend also the size of cache / the performance of disk .....
- if the ldap client can use vlvcontrol and if you execute always the same specifics searches you could use the vlvindex with a search filter which match exactly vlvfilter, see in Admin Guide chapter: Managing Browsing Indexes
-but now if you have very big index you could increase the nsslpad_db_page_size ( 8k by default, valid range 512 bytes to 64 KB ) to have a maximum of candidate list in one dbpage
- there are no good value but a value > 100 000 in the majority of case is already too high, (It is better to reorganize the data structure which is not any more adapt for ldap Directory , difficult operation and not easy with the evolution of the ldap directory )
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