ns-slapd oomkilled when using ipa migrate-ds to migrate from openldap to Identity Management

Issue

• While using ipa migrate-ds to migrate from OpenLDAP to IPA, the ns-slapd process grows to fill all physical RAM, and is eventually oomkilled.

  PID  USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+     COMMAND
  3776 dirsrv    20   0 5043m 3.9g  17m S 90.0 25.1    180:10.20 ns-slapd
  
  2011-12-28T06:30:04.235508-06:00 authtest kernel: Out of memory: 
  Kill process 3776 (ns-slapd) score 960 or sacrifice child
  
  2011-12-28T06:30:04.235511-06:00
   authtest kernel: Killed process 3776, UID 201, (ns-slapd) 
  total-vm:22793688kB, anon-rss:15676664kB, file-rss:1720kB
  

• Errors from the end of the ipa migrate-ds debug log:

  ipa: DEBUG: handshake complete, peer = 10.0.0.76:443
  ipa: DEBUG: Caught fault 4203 from server https://authtest.example.com/ipa/xml: Can't contact LDAP server:
  ipa: DEBUG: Destroyed connection context.xmlclient
  ipa: ERROR: Can't contact LDAP server:
  

• Verified via tcpdump that LDAP queries to source LDAP server are returning quickly, ruling out the source server as a cause.