---
name: "mdb_env"
section: "3"
platform: "linux"
package: "lmdb-doc"
version: "0.9.31-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/mdb_env"
---

# mdb\_env(3)

Environment Flags

## NAME

mdb\_env - Environment Flags

## SYNOPSIS

### Macros

\#define **MDB\_FIXEDMAP**   0x01\
 \#define **MDB\_NOSUBDIR**   0x4000\
 \#define **MDB\_NOSYNC**   0x10000\
 \#define **MDB\_RDONLY**   0x20000\
 \#define **MDB\_NOMETASYNC**   0x40000\
 \#define **MDB\_WRITEMAP**   0x80000\
 \#define **MDB\_MAPASYNC**   0x100000\
 \#define **MDB\_NOTLS**   0x200000\
 \#define **MDB\_NOLOCK**   0x400000\
 \#define **MDB\_NORDAHEAD**   0x800000\
 \#define **MDB\_NOMEMINIT**   0x1000000\

## Detailed Description

## Macro Definition Documentation

### #define MDB\_FIXEDMAP 0x01

mmap at a fixed address (experimental)

### #define MDB\_NOSUBDIR 0x4000

no environment directory

### #define MDB\_NOSYNC 0x10000

don't fsync after commit

### #define MDB\_RDONLY 0x20000

read only

### #define MDB\_NOMETASYNC 0x40000

don't fsync metapage after commit

### #define MDB\_WRITEMAP 0x80000

use writable mmap

### #define MDB\_MAPASYNC 0x100000

use asynchronous msync when **MDB\_WRITEMAP** is used

### #define MDB\_NOTLS 0x200000

tie reader locktable slots to **MDB\_txn** objects instead of to threads

### #define MDB\_NOLOCK 0x400000

don't do any locking, caller must manage their own locks

### #define MDB\_NORDAHEAD 0x800000

don't do readahead (no effect on Windows)

### #define MDB\_NOMEMINIT 0x1000000

don't initialize malloc'd memory before writing to datafile

## Author

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