core/src/main/java/com/orientechnologies/orient/core/db/ODatabasePoolBase.java
public DB acquire(final String iName, final String iUserName, final String iUserPassword,
      final Map<String, Object> iOptionalParams) {
    setup();
    return dbPool.acquire(iName, iUserName, iUserPassword, iOptionalParams);
  }
public DB acquire(final String iName, final String iUserName, final String iUserPassword,
      final Map<String, Object> iOptionalParams) {
    setup();
    return dbPool.acquire(iName, iUserName, iUserPassword, iOptionalParams);
  }
Acquires a connection from the pool specifying options. If the pool is empty, then the caller thread will wait for it.

@param iName
Database name
@param iUserName
User name
@param iUserPassword
User password
@return A pooled database instance