> ## Documentation Index > Fetch the complete documentation index at: https://flextable-docs-oracle-client-choice.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Oracle > Connect to Oracle in FlexTable - choosing an Instant Client, using your own installation, and fixing common login errors. Oracle works like the rest of FlexTable ([connect](/connecting), [browse and edit](/browse-and-edit), [query](/query-editor)). This page covers what is specific to Oracle, and most of that is the **Instant Client** - a library Oracle requires and the other engines do not. ## Oracle needs a client library Oracle connections go through Oracle's own **Instant Client**. FlexTable does not ship it inside the installer; the connection form shows a **Download driver** step when the client you selected is missing, and fetches it for you. The download is Oracle software governed by Oracle's licence, which is linked next to the download button. ## Choosing a client version **Start on 23ai and only change this if a connection is actually refused.** An older server does not on its own need an older client - we have connected the 23ai client to an Oracle 11.2 server without trouble. What decides the handshake is the logon-protocol policy configured on each side and the password verifier stored for your account, none of which you can tell by looking at the server's version number. So there is nothing to work out in advance: try, and change only if Oracle says no. | Client | Reach it is published for | How you get it | | ------------------ | ------------------------- | ------------------------------------------------------------------------------------- | | **23ai** (default) | Oracle 19c and newer | Downloaded for you. On Apple Silicon this is the only client Oracle publishes at all. | | **19c** | Oracle 11.2 to 23ai | You install it (see below). No 19c client exists for Apple Silicon. | | **11.2** | Oracle 10g and 11g | You install it (see below). Windows and Linux only. | The "reach" column is Oracle's support statement, not a promise that anything outside it will fail - in practice 23ai often works well past it. Treat it as the order to step down in when a login IS refused: see [Older servers that reject the login](#older-servers-that-reject-the-login). ## Using your own Instant Client FlexTable distributes client 23 only. To use 19 or 11.2: 1. Download **Instant Client Basic** for your platform from [Oracle](https://www.oracle.com/database/technologies/instant-client/downloads.html). 2. Unpack it anywhere you like. 3. In the connection's Oracle options, select that client version and point FlexTable at the unpacked folder - the folder that directly contains `libclntsh.so` (Linux), `libclntsh.dylib` (macOS), or `oci.dll` (Windows). If the folder does not hold that library, FlexTable says so rather than quietly falling back to a different client. It also checks the version that actually loaded: if you select 19 and the folder holds a 23 client, the connection stops with an explanation instead of failing later with a confusing login error. ## Changing the client version needs a restart Oracle's client library loads **once per application session**, so a connection cannot switch to a different version while FlexTable is running. When you change it, FlexTable asks you to restart, and offers to do it for you. ## Linux The Instant Client links against `libaio`. If a connection fails with `DPI-1047`, install it: ```bash theme={null} sudo apt install libaio1 # Debian, Ubuntu (on 24.04 the package is libaio1t64) sudo dnf install libaio # Fedora, RHEL ``` ## Older servers that reject the login A login can be refused with **ORA-28040** or **ORA-28041** when the client and the server cannot agree on a login protocol - typically a client or server configured to demand a newer protocol than the other side offers, or an account still carrying only an old password verifier. Work through these in order: 1. **Select an older client** - 19 for most cases, 11.2 for 10g and 11g servers - then restart. 2. If the login is still refused, enable **Allow legacy Oracle authentication** in the connection's Oracle options and restart. Legacy authentication makes the client accept old, weak password verifiers. Because Oracle's client loads once per session, it lowers the standard for **every** Oracle connection until you restart FlexTable - not just this one. Turn it on only for a server that needs it, and prefer an encrypted connection when you do. ## Databases and schemas Oracle's **database** selector lists pluggable databases (PDBs) and the **schema** selector lists users, so browsing works the same way as Postgres's database and schema pair. Schemas Oracle maintains itself are hidden until you turn on system schemas. ## Troubleshooting | You see | What it means | | --------------------------------------------- | ------------------------------------------------------------------------------------------------------------- | | `ORA-28040` or `ORA-28041` | Client and server disagree on the login protocol. Try an older client, then legacy authentication. | | `DPI-1047` | The client library could not load. On Linux, install `libaio`. | | Instant Client is not installed | The version this connection selected is not present. Download it, or point FlexTable at your own folder. | | A different client version is already loaded | Oracle loads one client per session. Restart FlexTable, then connect. | | The loaded client is not the selected version | The folder you pointed at holds a different version. Point at a matching one, or select the version you have. |