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CrosDB Database is a collection of tables.

Steps to define a database

  • Decide where to store the database: on disk, on ramdisk or in memory.
  • Decide the database is accessed by single process or multiple proceses.
  • Use cross_dbCreate to create or open database.
  • Use Schema to define table scheam.
  • Decide Table Primary Key: fields list, index type.
  • Use cross_dbTblCreate to create or open table with schema defined above and provide the primary key.
  • Decide how many secondary indexes: fields list, index type, whether unique.
  • Use cross_dbIdxCreate to create table secondary index.

Storage Mode

On-Disk Database

  • Database is on persistent disk, survive with power cycle.
  • If you have data persistency requirements, please use this type. The performance is ver high.
  • You need use transaction to guarantee data integrity even power cycle happened.

RamDisk Database

  • Database is on ramdisk tmpfs ramfs(CROSS_RAMDISK), survive with process restart, lose after power cycle.
  • This is designed for process runtime databse and the transaction performance is higher than On-Disk database.
  • The performance is almost the same with In-Memory database.
  • For Linux embedded system, this is the prefered database as the database can be viewed and stayed there even process crashed.

In-Memory Database

  • Database is in memory(CROSS_INMEM), survie when process is runnig, lose after process terminates.
  • This is not recommented, but if you don't want the process runtime database visible, it's the solution.

Access Mode


  • Database is accessed exclusively by single process with best performance.


  • Databse is accessd by multiple process(CROSS_SHARED), then performance will be low as file lock is used to access DB which can recover lock when process crashed.


Database is accessed exclusively by default.


  • Database is stored on disk by default.
  • If path(absoulte or relative) is not provided, DB is stored in current folder.


#define CHECK(ret,str)  \
    if (ret < 0) {  printf (str": %s\n", cross_errMsg(ret)); return -1; }

cross_ret       ret;
cross_db_h      hDb;

// Create on disk database in current folder for single process access
ret = cross_dbCreate (&hDb, "ondiskdb", 0);
CHECK (ret, "Failed to create database");

// Create on disk database for multiple process access
ret = cross_dbCreate (&hDb, "cdb_data/shareddb", CROSS_SHARED);
CHECK (ret, "Failed to create database");

// Create ramdisk database for single process access
ret = cross_dbCreate (&hDb, "/tmp/cdb_data/mydb", CROSS_RAMDISK);
CHECK (ret, "Failed to create database");

// Create in memory database
ret = cross_dbCreate (&hDb, "imdb", CROSS_INMEM);
CHECK (ret, "Failed to create database");