11. Improving Import Performance

Very large entry sizes or a large number of entries can negatively impact server performance during import operations. Both Directory Server settings and operationg system settings can be tuned to improve performance for imports.

11.1. Importing Entries with Large Attributes

The nsslapd-cachememsize attribute defines the size allowed for the entry cache.
The import buffer is automatically set to 80% of the cache memory size setting. If the memory cache is 1GB, for example, then the import buffer is 800MB.
When importing a very large database or entries with large attributes (often with values like binary data like certificate chains, CRLs, or images), then set the nsslapd-cachememsize attribute high enough so that the import buffer has enough memory to process the entries.

11.2. Importing Large Numbers of Entries

When there are a large number of entries to be imported, the operating system itself may hit performance limits on what it allows the Directory Server to do. This is particularly true on x86 systems. This can cause import operations to fail because of resource constraints.
If necessary, set the system ulimit value to the maximum number of allows processes for the system user.
For example:
[root@server ~]# ulimit -u 4096
Then run the import operation.