After applying maintenance to LDAP server the region would not start.
ABEND=S000 U4038 REASON=00000001 after maintenance
Error message in dump showed
CEE3501S The module libslapd.dll was not found.
slapd.env was the default version supplied with the product instead of locally modified version.
The default slapd.env pointed to incorrect directories in the path and libpath parameters.
Using the correct, locally modified, slapd.env resolved the abend.